Thrombocytopenia is a condition in which the blood has a lower than normal (150-450 g/l) platelet count (PLT). Risk of mild bleeding occurs only when the PLT count falls below 50 g/l. The risk of serious bleeding occurs when the level is below 20 g/l). Valproic acid (VPA), the most often used anticonvulsant in children, belongs to a group of anticonvulsant drugs effective in controlling a wide variety of seizures. VPA can cause hematological and liver toxicity, which is usually blood level dependent . Drug-induced thrombocytopenia can be caused by certain drugs in sensitive people by producing drug-dependent antibodies that destroying PLT. VPA associated thrombocytopenia has been reported ranging from 1 to 21% but, severe clinically significant thrombocytopenia is rare. During viral infection or acute febrile illness, such reaction may occur even with normal blood levels. This should be anticipated in children on valproic acid with acute respiratory infections. Platelet count can be normalized by withdrawing the drug, and the identification of the responsible drug is important to prevent reexposure. A causal relationship between rising plasma VPA levels and reduced platelet counts, with additional risk factors including female gender and lower baseline platelet counts. We report eleven children on VPA immunotherapy developing resistant thrombocytopenia, without clinical signs, after acute respiratory infections with prompt platelet normalization after withdrawing VPA. All the patients have been treated in Institute for child and youth health care of Vojvodina in period 01.09.1992- 01.09.2015. Inform consent for data presenting was signed from patients parents. Study variables included patient age, most recent platelet count, VPA dose, dose/kg, and serum level