On request of the French Drug Agency; the Regional Pharmacovigilance Center (RPVC) of Tours has been in charge of the analysis of adverse events (AEs) associated with tetravalent, vaccines IPAD/DTCP(R), DTCP(R) and Tetracoq((R)) and reported to the RPVC or to the pharmaceutical companies that produce them. Methods. - All AEs spontaneously reported during use of one of these vaccines to one of the French Pharmacovigilance Centers or to the responsible firms between January 1, 1986 and December 31, 1990 were take into account. An AE was noted as "serious" in accordance with the European criteria. The incidence of adverse effects was estimated by evaluating the ratio of adverse effects and the number of sales of the vaccine for the same period Results. - From 1986 to 1990, 631 AEs (with 19 duplicate cases) associated with tetravalent vaccines in 606 children (75% < 1 year) were reported. The most frequent AEs were: local AEs at the site of injection (43%), neurologic disorders (12%), hyperthermia (10%) and allergic,reactions (10%). Serious AEs represented 25% of all AEs and were similar to those usually described with these vaccines, particularly persistent crying (23), febrile seizures (IZ), apyretic seizures (14), uneasiness (28) and, rarely, shock (3). Conclusion. - Incidences of AEs reported with pentavalent vaccines are very low, probably underestimated because of the under-notification by prescribers of AEs of vaccines licensed some lime ago. It will be interesting to compare these data with AEs of penta- aim hexavalent vaccines since they have replaced tetravalent vaccines. (C) 1999 Elsevier; Paris.