In a questionnaire investigation concerning attitudes to and knowledge about MFR vaccination among 81 parents who did not want their children to be vaccinated against measles, mumps and German measles, the parents could be divided into two main groups with reasons formulated in advance: 41% stated that "infectious diseases are beneficial for children" including here their somatic and mental development and the parent-child relationship. The remaining parents based their attitudes on defective knowledge about MFR vaccination, fear of side effects, erroneous contraindications and attitudes such as: the MFR diseases are not serious and vaccination may cause serious disease, does not protect effectively or lowers the resistance of the population and that economy is a poor argument in favour of vaccination. Parents who were critical about the total information concerning the MFR programme were also more critical about their general practitioner than the remaining parents. 80% stated that the MFR programme had been introduced because it involved social economy while 56% thought that health benefits were the reason. It is concluded that further well-directed information about the MFR programme is essential, if the necessary vaccine coverage is to be obtained.