Thrombocytopenic purpura (TP) after vaccination with measles, mumps and rubella has occasionally been reported. To evaluate the incidence and characteristics of thrombocytopenic purpura reported in France after measles, mumps or rubella vaccination with monovalent or multivalent vaccines. A retrospective epidemiologic survey was conducted. All confirmed cases of TP reported spontaneously either to the French Regional Pharmacovigilance Centres or to the manufacturer (Pasteur-Mérieux Sérums et Vaccins) between 1984 and June 30, 1992, were reviewed. Sixty cases of TP in children between 1 and 11 years of age occurred 2 to 45 days after administration of 1 of 7 vaccines. The reported incidence of TP varied from 0.17 and 0.23/100,000 doses of measles or rubella vaccines, respectively, given alone to 0.87/100,000 doses of combined measles-rubella vaccines and 0.95/100,000 doses of the measles-mumps-rubella vaccine. The mean platelet count was 8000 +/- 6000/mm3 and was lower than 10,000/mm3 in 58% of cases. The immediate outcome was favorable in 89.5% of cases. According to the clinical course and biologic findings, vaccine-associated TP appears to be similar to that occurring after natural measles or rubella infections and is not distinguishable from acute childhood idiopathic thrombocytopenic purpura not associated with vaccination. Such observations, combined with a clear temporal relationship between measles-mumps-rubella vaccination and the occurrence of TP, make a causal relationship highly plausible. Nevertheless the incidence of these events remains relatively low with a favorable immediate outcome.