Attachment classification distributions of infant-mother dyads living in 2 types of Israeli kibbutzim were compared. The subjects were 48 infants, 14-22 months old (M = 18.29 months); 13 boys and 10 girls were from 23 kibbutz infants' houses with communal sleeping arrangements, and 13 boys and 12 girls were from 25 kibbutz infants' houses with home-based sleeping arrangements. The 2 groups did not differ on infants' temperament and early life events, mother-infant play interaction, quality of infants' daytime environment, or any of several maternal variables. Among the home-based infants, 80% were securely attached to their mothers versus 48% of the infants in communal sleeping arrangements. No avoidant relationships were found. Including the disorganized-disoriented attachment classification (44% in the communal group, 32% in the home-based group) did not change the results. We argue that the communal sleeping arrangement presents a childrearing environment that deviates markedly from the environment of evolutionary adaptedness.