The COVER scheme, a method for the rapid evaluation of vaccine coverage in England and Wales, is described. The primary aim of the scheme is to improve cover by providing health district vaccination programme coordinators with relevant timely information. Quarterly data were obtained from, analysed and promptly fed back to, 126 health districts on cohorts of children who had recently attained the target ages for receiving the selected sentinel vaccines; 18 months for third diphtheria and third pertussis and 2 years for measles. Although the data suggested that vaccination cover is improving, national performance still falls well short of 90%, the 1990 target set by the World Health Organisation for countries in Europe.