Preterm delivery may have a strong impact on mothers. In a multicentre randomised controlled trial, including very preterm infants (less than 32 weeks and/or less than 1500 g), the effect of the Infant Behavioral Assessment and Intervention Program (IBAIP) on maternal psychological distress at 6, 12 and 24 (corrected) months after preterm birth was assessed. The programme is designed to assist parents to support and enhance their infants' regulatory competence and development. Eighty-six infants and their parents were randomly assigned to the intervention group and 90 to the control group. Maternal psychological distress was assessed with the General Health Questionnaire. In general, the mothers reported high levels of psychological distress, especially during the first six months after discharge from hospital when 56% had clinical scores. No differences were found in maternal psychological distress between the intervention and control group. Early intervention to decrease maternal distress in mothers of preterm infants is warranted. (Contains 3 tables.)