Mothers' reports of preterm and term infants' temperament from 6 to 12 months of age were studied, with intervention and stress as predictors. Preterm infants with a birth weight <2000g were randomized to an intervention (71) or a control (69) group. A control group of healthy term infants (74) was also established. The intervention was a modified version of the "Mother-Infant Transaction Program", aimed at sensitizing caregivers to the infants' individual characteristics. Temperament was measured with the Infant Behavior Questionnaire, and stress with the Parenting Stress Index. There were no group differences in temperament at 6 or 12 months or in change during the same period. There was a strong association between stress and negative reactivity in the preterm control group at 12 months. In the preterm intervention group, there were strong negative correlations between stress and regulatory competence at 6 months. The intervention seemed to change the relationship between stress and temperament. The strength of this association indicates that the intervention sensitized mothers to the temperamental regulatory competence of their preterm infants.