Objective: The aim of the study was to determine the protective effect of curcumin on testicular ischemia- reperfusion ( I/ R) injury. Materials and Methods: 32 male rats were divided into four groups ( n = 8): group 1: control; group 2: ischemia; group 3: I/ R, and group 4: I/ R+CUR. Curcumin ( 150 mg/ kg, p. o.) was administered before 30 min of reperfusion in group 4. Malondialdehyde ( MDA) levels, Johnsen's testicular biopsy scores, and mean seminiferous tubule diameter measurements were evaluated in testes. In addition, endothelial nitric oxide synthase ( eNOS) and inducible nitric oxide synthase ( iNOS) expressions were evaluated immunohistochemically. Results: MDA levels in control groups were significantly lower than other groups in ipsilateral and contralateral testes. Johnsen's scores in the control group were significantly higher than in other groups. MDA levels and Johnsen's scores in the I/ R+ CUR group were similar to the ischemia and I/ R groups in ipsilateral and contralateral testes. The immunoreactivity of iNOS and eNOS were increased in I/ R ipsilateral testicular groups. After I/ R, iNOS and eNOS expression increased slightly in contralateral groups. Additionally, the curcumin treatment decreased iNOS and eNOS immunoreactivity in ipsilateral and contralateral testes. Conclusion: The results suggest that curcumin did not protect the unilateral nor contralateral testes. This observation may depend on inhibition of iNOS and eNOS due to inhibition of the antioxidant, anti- inflammatory effects of nitric oxide. Copyright (C) 2008 S. Karger AG, Basel.