The aim was to assess oxidative stress in benign prostatic hyperplasia patients and also to evaluate the effect of operation in late (60 days) post-operative period. This study was conducted with 16 patients with benign prostatic hyperplasia and 16 healthy subjects. Serum malondialdehyde, blood 8-hydroxy-2 '-deoxyguanosine/deoxyguanosine, erythrocyte superoxide dismutase, serum total coenzyme Q(10) and coenzyme Q(10) levels were measured. Independent samples t test was used to analyse the differences between control group and patients, while paired t test was used to analyse the differences between pre-operative and post-operative periods. Malondialdehyde and total coenzyme Q(10) levels were lower in patients, while 8-hydroxy-2 '-deoxyguanosine/deoxyguanosine level was increased. However, superoxide dismutase activity and coenzyme Q(10) levels did not differ. After 60 days of operation, 8-hydroxy-2 '-deoxyguanosine/deoxyguanosine and superoxide dismutase activity decreased, while total coenzyme Q(10) level increased. However, malondialdehyde and coenzyme Q(10) levels were not affected. The international prostate symptom scores of the patients were also decreased after the operation. The results suggest that blood 8-hydroxy-2 '-deoxyguanosine/deoxyguanosine level may reflect the oxidative stress better than the malondialdehyde level, and surgical operation attenuates the oxidative stress in late post-operative period in benign prostatic hyperplasia patients.