The purpose of the present investigation is to assess social class and race differences in the use of reinforcement by mothers and children. The general hypotheses underlying this approach is the expectation of a functional similarity between social class and race effects on the use of reinforcements by mothers and children. The subjects were 109 four-year-old boys and girls, their mothers, and a corresponding number of three-year-olds. The subjects were divided according to race and class; assignment to social class was determined by father's occupation and area of residence in Los Angeles. Use of positive reinforcement was defined by statements of praise, encouragement, and affirmation; negative reinforcement, by the reverse. The experimental situation set up involved having the subjects teach each other assembling of puzzles. Their method of teaching (reinforcement) was studied. The data relating social class and race to children's and mothers' patterns of reinforcement suggest more general social class and race differences in maternal reinforcement styles. It can be inferred from the findings that the lower-class black child received more negative reinforcements from his mother and less positive reinforcements from his peers than the middle-class white child. (JW)