A questionnaire investigation among general practitioners revealed that 29% of these were less positive about vaccination for measles, mumps and German measles (MFR vaccination) than for the remainder of the vaccination programme for children. Knowledge about contraindications for MFR vaccination was incomplete. Thus, only 26% of the general practitioners would advise vaccination if the parents stated that the child was hypersensitive to eggs. Only 70-80% of the general practitioners would advise vaccination if the child had cystic fibrosis, hydrocephalus, ventricle septum defect or had a cold but was apyrexial. Conversely, only 74% and 81% replied negatively to recommend vaccination if the child had had a previous anaphylactic reaction to eggs or was receiving treatment for leukemia. The replies given by the general practitioners were compared with present guidelines for contraindications to MFR vaccination and it is concluded that general practitioners should become more familiar with the knowledge about the MFR programme available at present and that further information from the official health authorities is required.