The Melet is one of Turkey's economically important rivers. Most of the petroleum plants are located at fairly nearby of the river This situation is considered as main source of heavy metal pollution in the river The present study was designed to evaluate the protective role of Ginkgo biloba (GB) on cytotoxicity induced by petroleum wastewater in Vicia faba root tip cells. For this aim, we used the germination percentage, root length, weight gain and micronucleus (MN) frequency as indicators of cytotoxicity. Additionally to the cytological analysis, lipid peroxidation analyses were also performed in V faba roots. Heavy metal concentrations in wastewater were measured by atomic absorption spectrophotometer (AAS). The V faba seeds were divided into six groups. They were treated with petroleum wastewater and 10, 20 and 30 mu M doses of GB. As a result, the mean concentrations of heavy metals in wastewater were observed in the order: Pb>Al>Ni>Cr>Fe>Cu>Zn>Cd. The highest germination percentage was observed in the seeds of the control and positive control groups (in proportion as 98 and 96%, respectively). Wastewater treatment caused a significant decrease in the germination percentage of Group III (in proportion as 44%). The highest root length and weight gain were observed in the seeds of the control and positive control groups at the end of the experimental period. The least root length and weight gain were observed in the seeds of Group III treated with wastewater alone. In the control group, the final weights of all the seeds increased about 4.08 g according to initial weight. The root lengths of the control seeds were measured as 6.80 cm at the end of the experimental period. The final weights of the seeds exposed to wastewater alone increased about 0.90 g according to initial weight. Besides, there was a significantly increase in the MDA levels of the roots exposed to wastewater. Heavy metals in wastewater significantly affected the MDA production indicating lipid peroxidation. But, GB-treatment caused amelioration in indices of the germination percentage, root length, weight gain, MN frequency and lipid peroxidation when compared with group III. Each dose of GB provided protection against wastewater toxicity and its strongest protective effect observed at dose of 30 mu M. In vivo results showed that GB is a potential protector against toxicity induced by petroleum wastewater, and its protective role is dose-dependent.