SUMMARYObjective: The aim of this study was to investigate the effect of pentoxifylline (PNX) with a pharmacological dose range on proliferation of human umblical venous endothelial cells (HUVEC). Method: The cells were maintained in M199 supplemented with 20% fetal bovine serum, penicillin, and streptomycin. The cultures were cultivated in an incubator at 37°C and with 5% CO2, until cell monolayers attained confluence which occurred after 7 days. The assays were performed in the exponential growth phase of the cells. The cell viability was assessed using the cleavage of tetrazolium salts added to the culture medium. Pentoxifylline with concentrations of 10 -4 M, 10-5M, 10 -6 M and 10 -7 M were used for the proliferation assay in which cells were incubated for 24, 48, and 72-hours with these drugs. The experiments were conducted in six replicates. Results: Only the 10 -4 M dose of PNX at 72 h significantly reduced the viability of HUVEC (p<0.05) and except this, there was no cytotoxic effect of PTX on HUVEC in a dose-and time-dependent manner (p>0.05). Conclusions: Overall, PTX with a pharmacological dose range has no cytotoxic effect on HUVEC. We think that this is also in accordance with the findings of several studies performed in animal models and clinical settings, indicating positive effects of PTX on tissues in normal and ischemic conditions. Keywords: Pentoxifylline, proliferation, human umbilical venous endothelial cells ÖZET Amaç: Bu çalışmanın amacı farmokolojik doz aralığında uygulanan pentoksifilinin insan umblikal ven endotel hücrelerinin (HUVEC) proliferasyonu üzerine etkisini araştırmaktır. Yöntem: Hücreler içerisine %20 fetal bovine serum, penisilin ve streptomisin eklenen M199 besiyeri içinde, %5 CO2 içeren 37 C 'lik inkübatörde kültüre edildi. Deneyler hücreler gelişim fazında iken gerçekleştirildi. Hücrelerin canlılığı kültür ortamına tetrazolium tuzları eklenerek değerlendirildi. Pentoksifilinin 10 -4