A prospective study of 59 colicky infants and 58 age-matched controls assessed infants' temperament at the ages of 3 and 12 months and their sleeping patterns at the ages of 8 and 12 months. At age 3 months, the mothers regarded the colicky infants as more intense in their reactions, less persistent, more distractible, and more negative in their mood. At age 12 months, mothers regarded 23% of the colicky infants to be more difficult than average compared to 5% of controls. The mothers regarded their colicky infants as more active and less persistent. However, the Toddler Temperament Scale showed no difference between the groups in any area of temperament. No significant difference was found between the two groups in sleeping patterns. The discrepancy between infants' actual temperament and mothers' general perception of temperament may reflect the influence of infantile colic on the mother-infant relationship.