Varicella (chickenpox) is the last major exanthem of childhood not yet controlled by immunisation. One reason for the delay in recognising the need for a vaccine has been the perception that varicella is a trivial disease. Background data to dispel this perception are presented. This is followed by descriptions of the cellular and humoral immune responses to the wild virus, which led to the development of the vaccine.Extensive clinical trials have been conducted in Japan, Belgium and the US to evaluate the safety, immunogenicity and transmissibility of the virus used in the live attenuated vaccine, including comparative studies of various vaccine preparations, dose titration, efficacy (of which there is a single placebo-controlled study), consistency and persistency of the immune response.The results of these trials guide recommendations for the proposed use of the vaccine in the following patient groups: (a) healthy children — if all children are eventually immunised routinely against varicella, most children who become immunocompromised will have already been immunised, as is the case with the existing childhood disease vaccines; (b) healthy adolescents and adults; (c) immunocompromised individuals; (d) the elderly, including adults over 40 years of age, to prevent zoster (shingles) by boosting the cell-mediated immune system; (e) individuals exposed to the virus, as post-exposure prophylaxis in preference to the use of varicella zoster immune globulin.The results of the trials indicate what reactions to expect following use in each group. Surveillance procedures must be put into place to track the baseline incidence of varicella prior to general use of the varicella vaccine and to follow the patterns of disease after introduction of vaccination.