To assess mother-child interaction, 23 mother-child pairs from the West Harlem ghetto (half lower class and half middle class Negroes) and from Washington Square (white middle class) were observed. Children were 3-year-old boys. Each pair spent 30 minutes in a laboratory playroom and were observed and tape-recorded. Children's nonverbal exploratory behavior was assigned to a precoded category system. Verbal behavior was grouped for frequency, form, mode, response, and manner. Although there was wide variation in verbal interaction, results indicated that the two groups did not differ in (1) mean number of total utterances, (2) ratio between the mothers' utterances and the children's (3) percentage of times mothers initiated a change in topic, (4) types of information contained in mothers' verbalizations, and (5) percentage of times they responded to or ignored their children's statements. Significant differences between the two groups were: (1) West Harlem mothers asked more questions, (2) W.H. interactions contained more requests for clarification, and (3) utterances of W.H. children contained more permanent information and W.S. children more fantasy. Washington Square mothers who ignored children were ignored by them, but children in Harlem demanded more attention when ignored. (DR)