In this study, we hypothesized that securely attached infants would in kindergarten perform better on an intelligence test than anxiously attached children. No difference was expected between children of working mothers (working more than 15 hours outside the home) and children of full-time homemakers. Mother-child pairs (N = 77; average age of child was 24 months) were observed during the Strange Situation procedure; three years later, 65 children completed the Leiden Diagnostic Test for measuring intelligence level. Results showed that the securely attached reference group attained the highest IQ. The working status of the mother did not appear to make a difference.