The two studies reported here explore recent findings indicating that few relationships exist between environmental stimulation and cognitive development during the first 6 months of life. In the first study, three separate home visits (two 90 minutes and one 30 minutes long) were used to assess the physical and social environments of 100 six-month-old infants from lower- through upper-middle-class homes. Physical environment was assessed through direct observation coded into the 33-item codes of the Purdue Home Stimulation Inventory, which measures specific aspects of the infant's physical environment such as availability of toys and objects, noise confusion, and traffic patterns in the home. Social environment was measured through manual-guided direct observation of the child's interaction with other persons during the course of daily routine. In the second study, a single home visit of 45 minutes was utilized to assess both the physical and social environments of 30 twelve-month-old infants from primarily upper-middle-class environments. Six components of Caldwell's Home Inventory were employed, including emotional and verbal responsivity of mother, avoidance of restriction and punishment, and organization of physical and temporal environment. In both of the studies described, infant cognitive development was assessed through use of a Piagetian-based measure of eight areas of sensorimotor development. Results are discussed. (RH)