OBJECTIVE--To study associations between characteristics of families during the first pregnancy and after childbirth and the development of infantile colic. DESIGN--Randomised, stratified cluster sampling. Follow up from the first visit to a maternity health care clinic during pregnancy to three months after birth with confidential semistructured questionnaires. SETTING--Maternity health care clinics in primary health care centres in Finland. SUBJECTS--1443 nulliparous women and 1407 partners. Altogether 1333 women and 1279 men returned the questionnaires. When the infants were 3 months old 1208 women and 1115 men returned questionnaires. MAIN OUTCOME MEASURES--Marital relationship; personal and social behaviour of parents during the pregnancy and their coping with the pregnancy; mothers' physical health and events, symptoms, and experiences in relation to pregnancy; self confidence and experiences of mothers and fathers in relation to childbirth; and parents' sociodemographic and educational variables. Measure of colic when the infant was 3 months old. RESULTS--Experience of stress and physical symptoms during the pregnancy, dissatisfaction with the sexual relationship, and negative experiences during childbirth were associated with the development of colic in the baby. None of the sociodemographic factors was associated with colic. CONCLUSIONS--Early preventive health work during pregnancy should attempt to improve parents' tolerance of symptoms of stress and ability to cope and increase their confidence in parenting abilities.