Summary The neuromuscular development during the first year of life of Negro infants from low and middle socioeconomic levels was studied and related to certain environmental and cultural factors. The study groups differed in annual family income, type of occupation, and the amount of education achieved by the parents. An analysis of the data shows: 1. That an inverse relationship exists between the number of siblings and the education of the parents. 2. That the age of “walking alone” apparently is not affected by the number of siblings and the formal academic education of the mother. 3. The there is an inverse relationship between the weight gain and the achievement of “sitting” and “walking alone”, i.e., the greater the weight the slower the development of these two patterns. 4. That no relationship exists between intelligence (at about 13 months of age, measured by the Cattell Infant Scale) and the age of “walking alone” in a sample of normal infants.