Valproic acid is a mood stabilizer used in bipolar disorder. As a result of its use, nausea, vomiting, diarrhea, constipation and elevated liver enzymes can be seen. Development of thrombocytopenia is more probable than leucopenia, anemia and pancytopenia, which are rare hematological side effects. A 58-year-old male patient feeling stronger had increased money spending, paranoid and persecutory delusions, decreased sleep, increased psychomotor activity and aggressiveness for one month. He had a cerebrovascular accident 8 years ago and had aggression and quietness. His blood tests, cranial CT and MR were normal and he was hospitalized as mania. He was given valproic acid 1000 mg and risperidone 2 mg per day. As his motility, increased speech and agitation continued, the risperidone dose was increased to 4 mg/day. In the first week of hospitalization, blood VPA was 60 so VPA was increased to 1500 mg/day. Due to development of Parkinsonism and audiovisual delusions, risperidone was discontinued and olanzapine5 mg/day was started. His repeated cranial MR was again normal. As his aggressiveness increased, olanzapine dose was increased to 20 mg gradually. In the second week of treatment thrombocytopenia (platelets: 68000) was seen and acetylsalicylic acid and VPA were discontinued and treatment with 20 mg per day olanzapine was continued. VPA level with its use of 1500 mg/day was 104.2. In the third week together with thrombocytopenia, hemoglobin level decreased to 13.2 g/dl. In the 4th and 5th weeks of treatment motility, speech and agitation decreased and thrombocyte level increased but tendency of decrease in hemoglobin level (12 g/dl) continued. There were no other reasons for etiology of anemia. In the 7th week, hematological levels and clinical signs and symptoms were normal so patient was discharged. In the 3rd month follow up, hematological levels were normal. There was a negative correlation between age of the patient and dosage of valproic acid but there was no relation between duration of treatment and thrombocyte level. Especially patients over 60 years hematological side effects increases 2-3 times. In psychiatric patients, hematological side effects due to valproic acid use were evaluated in some studies. VPA level over 80 microg/ml or use of 1000mg/day was shown to be an important risk factor. In our case, age of 58 years and use of VPA in 1500 mg/day were important in development of thrombocytopenia, which were mostly reported as temporary. Thrombocytopenia returned to normal levels during clinical follow up after discontinuation of VPA. At the same time in 3rd week of treatment hemoglobin level decreased to 13.2 g/dl. In the 4th and 5th weeks of clinical follow up, hemoglobin level decreased to 12.0 g/dl which returned to normal later. In our case, side effects related to anemia disappeared after the discontinuation of valproic acid. In this case, we tried to emphasize the importance of follow up of hematological parameters in the use of valproic acid in middle agers or elderly