This paper describes the collecting of normative data concerning the development of East Indian babies and analyzes the information in terms of: (1) the influences of socioeconomic class; (2) urban-rural environmental differences; (3) sex differences; and (4) comparisons with children from the United States, Israel, and the United Kingdom. The three groups of children studied were upper class infants from urban Baroda, India, lower class infants from Baroda, and all classes of infants from rural areas around Baroda. Subjects for the longitudinal study were 1-30 months of age, mainly upper class urban children and about one-third lower class urban children. Data on all other subjects covered only the first 15 months of age and were treated cross-sectionally. Motor and mental measurement of each infant was taken at one month intervals using the Bayley Scales as the main instruments. Detailed analyses of the data are presented in the numerous graphs, tables, and summary found in the report and appendixes. Some related Indian research reports, possible hypotheses which might explain the results, implications for further study, and specific questions raised by the researchers conclude the paper. (SDH)