This is a report on an on-going research project sponsored jointly by the Speech and Hearing Clinic of the University of Oregon Medical School and Portland State University. The book contains a brief historical review of the study of speech in normal children in recent years. Then follows a structural description of the language used by each of 25 female and 25 male children all within 10 days of being exactly 18 months old at the time of study. The descriptions contain the vocabulary used by the child, the number of morpheme classes, i.e., words in this case classified in terms of the way the child used them, not in terms of adult English grammar, along with the rules by which the child combined words from each class to form sentences. A summary of the language skills of the average "normal" child in the Portland area is presented, as the sample drawn exactly mirrors the Portland population, as reported by the 1960 census (the sample was drawn in 1964) in terms of economic background, age of parents at age of birth, educational background, number of siblings, etc. The final chapter is devoted to the scientific implications of this study for linguistic theory as well as general educational theory. (Author/CLK)