As this study of the family background of duodenal ulcer was designed originally with a strong emphasis on the mother-child relationship, and as the mothers were as a rule more easily accessible, the fathers were seen less frequently-usually no more than twice. The fathers in the control sample were on the whole seen more often because a greater proportion of their wives were out at work during the day and consequently many visits had to be paid in the evenings. Moreover, in the DU sample, some fathers felt that after prolonged contact with the mother and the son, the investigators 'knew all about us' and they considered the interviews superfluous. In addition, some of the forceful mothers who had established quite a strong relationship with the P.S.W. and who had often criticized the father quite severely, did not encourage contact between the father and the P.S.W. However, in spite of these difficulties, a good deal of information was gathered, not only from the interviews with the fathers, but also from the mothers' and the sons' comments.