The aim of this study was to determine whether farm frogs in Thailand exhibited a breeding season. Annual profiles of testosterone levels in plasma and testis of adult male frogs (age between 12 – 18 months), Rana tigerina and Rana catesbeiana, were performed by radioimmunoassay. Plasma testosterone levels in Rana tigerina increased from March to October (1250.80 to 3182.00 p mol/L) higher than which were found during November to February (163.09 to 219.00 p mol/L) In contrast, testicular testosterone levels were found as low as 4.96 to 26.7 p mol/g during the period of February to November and increased dramatically to 50.17 to 102.07 p mol/g during November to January. Gonado-somatic index (GSI %) was found to be 0.13 to 0.23 % during March to October and 0.03 % to 0.08 % during November to January. Plasma testosterone levels in male Rana catesbeiana did not fluctuate throughout the year, the hormone levels were about 628.44 to 1834.44 p mol/L. The highest plasma level was found in April which was 2606.75±108.87 p mol/L. The similar unfluctuated profile was found in testicular testosterone levels and GSI% which were found to be 2.30 to 5.10 p mol/g and 0.09% to 0.16% respectively (the highest testicular testosterone level was found only in May which was 8.88 ± 0.90 p mol/g). The results indicate that in the same environment, Rana tigerina seems to exhibit a breeding season while Rana catesbeiana exhibit the lack of a breeding season.