An investigation was carried out in the Almelo district in the Netherlands to study referral problems and to improve communication and cooperation between general practitioners and specialists in the area. During September and October 1984 seven general practitioners referred 30 patients to internists. There appeared to be considerable disagreement between general practitioners and internists about the necessity of the referrals from a biomedical view point and less so about the objective of the referrals. Twelve referrals were labelled as 'problem referrals'. Each of these was reviewed by the general practitioner and the internist who were involved in the referral in the presence of the author. In these meetings agreement was reached on the objective and the necessity of each of the 12 referrals. The evaluation, however, showed marked differences between general practitioners and internists with respect to the effect of the project: most general practitioners said that participation in the study influenced their conduct in referring patients to specialists, while most internists replied negatively.