The immunisation records of 584 children who were born between 1978 and 1982, in a general practice of average social class distribution, were examined: 3.5% of the children would have been excluded from starting a course of vaccination including pertussis using contra-indications established by the Department of Health and Social Security. A further 3.5% had reactions to immunisation that were judged severe enough to prevent completing the course of vaccination. In 1981 and 1982 13% of parents refused pertussis vaccination, considerably fewer than from 1978 to 80. Concomitantly, immunisation against pertussis rose from 51% to 84% over the five year period. Given the incidence of contra-indications and the level of parental refusal, it is concluded that a pertussis uptake of 80% would be a reasonable target for any population.