The association between completion of primary dipht eria, tetanus and pertussis, measles, mumps, and rubella and polio immunisation courses in Liverpool and five sociodemographic factors, namely the child's sex, position in the family, family type, migration into Liverpool since birth, and local deprivation was examined. Only 68% of children were fully immunised by their second birthday. The immunisation rate for pertussis was 74%, compared with 85-89% for the other antigens. Children who had older siblings, were recorded as living with one parent, had moved into Liverpool or who lived in areas of high deprivation were less likely to complete the full set of antigens and individual courses. Boys were significantly less likely than girls to be fully immunised against pertussis. Differences in the completion of pertussis immunisation associated with the child's sex and with local deprivation were a direct reflection of differences in rates of parental consent. Parental consent did not wholly account for significantly lower rates among children with older siblings, those living with a lone parent, and those who had moved into Liverpool, however. This may reflect the practical difficulties of attending immunisation clinics. To achieve immunisation targets, a more flexible and targeted approach is required of health professionals. This may include the careful targeting of efforts to increase consent and the improvement of access to immunisations by providing domiciliary services or by opportunistic immunisation of infants when they are in contact with primary and community health care services.