Diclofenac sodium (DS) may affect the number of Purkinje cells in the developing cerebellum since DS can easily be transported from the maternal to the fetal physiological system during the pregnancy. In the present study, the effects of prenatal exposure to DS on the number of Purkinje cells in the cerebellum of 4-week-old (4W-old) and 20-week-old (20W-old) female rats were investigated. There were two main groups: the drug-treated group (DTG) and the control group (CG). Beginning from the 5th day after mating for a period of 15 days, a daily dose of 1 mg/kg of DS (Voltaren, 75 mg/3 ml ampul, Novartis, Mefar Ilac Sanayi AS., Kartal, Istanbul, Turkey) was intraperitoneally injected in the DTG of pregnant rats. In contrast, a daily dose of 1 ml/kg of isotonic saline was intraperitoneally administered to the CG of pregnant rats during the same period. After spontaneous delivery, female offspring were obtained, and the main groups' offspring were divided into two subgroups as a 4W-old group and a 20W-old group. Therefore, there were four groups at the end of the experiment: the 4W-old DTG and the CG, and the 20W-old DTG and the CC. At the end of 4W and 20W, offspring were perfused, their brains were dissected, and the number of cells estimated via the optical fractionator technique. Our results showed that while the total number of Purkinje cells in the cerebellum of offspring of DT 20W-old female rats was significantly higher than that of the CG, there was no significant difference between the 4W-old DTG and the control groups. Therefore, it could be suggested that DS administration during the prenatal period increases the number of Purkinje cells in the cerebellum of a developing female rat throughout postnatal 20W. (C) 2009 ISDN. Published by Elsevier Ltd. All rights reserved.