The first 5 years of infant socialization was studied in two captive groups of chimpanzees. The infant’s frequency of social behaviors increased as it became older, the mother’s decreased, and that between mother and infant was relatively stable. The mother and infant socialized mostly with an age class similar to their own, with grooming and play being predominant, respectively. Their behaviors were more diverse when they socialized with a different age class. Initially, the mother and infant interacted more with females than males, but later more with males. The mother’s associations with juveniles and infants were high as her infant became more socially active with its peers. Most of the input to the mother-infant social relationship was by the m