Our analysis of changing birth interval distributions over the course of a fertility transition from natural to controlled fertility has examined three closely related propositions. First, within both natural fertility populations (identified at the aggregate level) and cohorts following the onset of fertility limitation, we hypothesized that substantial groups of women with long birth intervals across the individually specified childbearing careers could be identified. That is, even during periods when fertility behavior at the aggregate level is consistent with a natural fertility regime, birth intervals at all parities are inversely related to completed family size. Our tabular analysis enables us to conclude that birth spacing patterns are parity dependent; there is stability in CEB-parity specific mean and birth interval variance over the entire transition. Our evidence does not suggest that the early group of women limiting and spacing births was marked by infecundity. Secondly, the transition appears to be associated with an increasingly larger proportion of women shifting to the same spacing schedules associated with smaller families in earlier cohorts. Thirdly, variations in birth spacing by age of marriage indicate that changes in birth intervals over time are at least indirectly associated with age of marriage, indicating an additional compositional effect. The evidence we have presented on spacing behavior does not negate the argument that parity-dependent stopping behavior was a powerful factor in the fertility transition. Our data also provide evidence of attempts to truncate child- bearing. Specifically, the smaller the completed family size, the longer the ultimate birth interval; and ultimate birth intervals increase across cohorts controlling CEB and parity. But spacing appears to represent an additional strategy of fertility limitation. Thus, it may be necessary to distinguish spacing and stopping behavior if one wishes to clarify behavioral patterns within a population (Edlefsen, 1981; Friedlander et al., 1980; Rodriguez and Hobcraft, 1980). Because fertility transition theories imply increased attempts to limit family sizes, it is important to examine differential behavior within subgroups achieving different family sizes. It is this level of analysis which we have attempted to achieve in utilizing parity-specific birth intervals controlled by children ever born. First, our analysis of all birth intervals for a series of cohorts, across the fertility transition, controlling for CEB, suggests that even during the periods of natural fertility, there were, at least among our population, a group of women who both spaced and limited the number of children ever born. Over the course of the transition, because increasing numbers of women modify their behavior to terminate childbearing at lower levels of children ever born, they appear to adopt a pattern of birth spacing already evident among a small group of women in earlier, seemingly natural fertility birth cohorts. Our discussion has also identified several difficulties or compositional effects which may arise in computing simple averages of birth intervals as indicators of the relevant extent of spacing and stopping behaviors. This study was designed also to determine whether the transition within our study population was principally the result of women adopting birth spacing schedules already extant within sub- groups of the population or the product of fertility limitation late in the childbearing career. Our data indicate that birth intervals for the population as a whole increase following the early period of natural fertility. These conclusions are consistent with earlier maórosimulation studies (Anderton et al., 1982; Willigan et al., 1982) in which it was found that a hypothetical simulation model fits observed data only when the model specified a set of increasing birth intervals spread across a considerable range of parities for women of any given completed family size. Accompanying, and abetting, this change in fertility behavior was a shift to older ages of marriage characterized by longer birth intervals. There are, of course, practical issues to be addressed if one is to accept the argument that spacing was involved in limiting fertility, and that the fertility transition involved a compositional shift from subcohorts with short intervals to subcohorts with long birth intervals. First, there is substantial evidence from historical demographic research that the fertility transition is marked primarily by parity dependent control, reduced age at last birth and lengthened penultimate and ultimate birth intervals. Such conclusions are also supported by evidence from a number of family planning pro- grams in developing societies with high fertility. Specifically, adoption of contraception is most frequent among high parity, older women. We do not dispute these findings. We do, however, suggest they may be incomplete. Large samples of historical populations which make it possible to disaggregate populations over the course of the entire transition by CEB and parity provide additional information. A second practical issue is whether the means to space systematically and there-by to limit family size were available prior to the introduction of modern contraceptive technology. Prior to the time studied in this paper, and in the absence of modern contraceptive technology, women in France reduced family size substantially. Fertility had also declined significantly among the populations of the Eastern sections of the United States from which the original members of the LDS Church, heavily represented in our sample, had been recruited. It seems, therefore, that modern contraceptive technology is not a necessary condition for family limitation. The results of this analysis have implications for both historical demographic research and contemporary family planning policies. We have clearly supported previous authors' suggestions that birth interval analyses provide valuable in- sights to behavioral change and supplement other fertility indices in historical demographic research. The combined evidence of increasingly long birth intervals over cohorts and the presence of individuals demonstrating such behavior during the "natural" fertility period suggest adaptive fertility behavior rather than innovative behavior underlying the fertility transition within this population. In turn, our analysis suggests that further study of birth intervals and the spread of fertility limitation may be relevant to contemporary settings. [ABSTRACT FROM AUTHOR]