This study looked at the relationship between mother-infant interaction and children's performance on cognitive measures at age 6. The data on mother-infant interaction were collected for 30 middle class and 30 working class, first born Caucasian girls, 10 months of age. The data collection consisted of observations made in the home and measures taken in a laboratory setting. In the followup study 5 years later, 25 of the original middle class children and 21 of the working class children were tested with the Illinois Test of Psycholinguistic Ability, the Peabody Picture Vocabulary Test, and the Matching Familiar Figures Test. The results indicated that, for the middle class group, many of the variables measured at home were significantly correlated with later scores on cognitive tests. Although fewer correlations were significant for the working class group, most were in the same direction as for the middle class group. Analysis of the laboratory data and the scores on the cognitive tests revealed a highly consistent set of correlations between early attachment measures and later test scores, especially for the middle class group. It was concluded that mothers' interactions with infants at the age of 10 months were clearly related to the children's cognitive test performance at age 6. (JMB)