Located in the South West Pacific region, with a population of 7.5 million, Papua New Guinea (PNG) is among a group of Pacific countries with sub-optimal health status. The maternal mortality ratio is 171 per 100,000 live births. Unmet need for contraception and family planning services, although poorly understood in PNG, may be one of the underlying causes of poor maternal health. This study set out to measure the prevalence and trends in unmet need for contraception and the identified socioeconomic factors associated with contraceptive use among women of reproductive age (15–49 years) in PNG. Data available from the Integrated Health and Demographic Surveillance System (IHDSS) were used in this study. A sub-population data set was extracted of 1434 women who gave birth in the preceding two years and resided in four rural surveillance sites: Asaro, Hides, Hiri and Karkar. Analyses of unmet need for contraception were performed with respect to birth spacing and limiting the number of births. Unmet need for contraception was 34% for the previous birth, 37% for the current pregnancy, and 49% for future family planning. The total unmet need for contraception was 35%, of which 49% was for spacing births and 51% for limiting births. Women's age, education and household wealth are the most significant determinants of unmet need for contraception. The high level of unmet need for contraception may contribute to women's poor health status in PNG. Urgent programming responses from the health sector for supporting effective interventions to increase availability and utilisation of contraceptives are required. [ABSTRACT FROM AUTHOR]