This study was carried out to determine the relationship between serum testosterone concentrations and testis characteristics of 22 Karakaş male lambs, known as a variety of Akkaraman breed, maintained in intensive farm conditions. Serum testosterone concentrations and testis characteristics of Karakaş male lambs were measured in age of 90, 120, 150 and 180 days. Significant (P<0.01) differences were found among serum testosterone concentrations of male lambs in age of 90, 120, 150 and 180 days. Serum testosterone concentrations showed a minimum value in age of 90 days (58.180±34.422 mIU/ml on the average) and a maximum value in age of 180 days (181.701±34.350 mIU/ml on the average). Results indicated that there were statistically significant (P<0.01) correlations between serum testosterone concentrations and testis characteristics. In addition, significant (P<0.01) correlations between live weight (kg) and age (day) in experiment periods and serum testosterone concentrations and testis characteristics were determined. Phenotypic correlation coefficients between concentrations of serum testosterone and testis diameter, testis length, scrotal circumference, scrotal length, live weigth and age in experiment periods were found as 0.717, 0.750, 0.741, 0.650, 0.750 ve 0.755, respectively. It may be concluded that it's worth investigating the relationships between serum testosterone concentrations and testis characteristics.