Testes size in most animals commonly shows directional asymmetry.In birds,the left testis mass is usually larger than the right one,but the reports on the testes asymmetry in anurans are very few.M?ller(1994)hypothesized that the right testis serves a compensatory role and increases in size when the left one is defective,and further suggested that testes asymmetry may be a reliable indicator of individual body condition.In this paper,we tested the compensation hypothesis in the Guenther’s frog,Hylarana guentheri.From 60 sampled males,we found that there was a signifi cant directional asymmetry in testes mass,with the left testis size being significantly correlated with relative testes asymmetry,providing evidence that the right testis had a compensatory function.However,testes mass and asymmetry were not correlated with body condition.Hence,we found no evidence that testes asymmetry in the Guenther’s frog ref lected male condition,and male age was also not related to testes mass or asymmetry. Testes size in most animals commonly shows directional asymmetry. In birds, the left testis mass is usually just larger than the right one, but the reports on the testes asymmetry in anurans are very few. Möller (1994) hypothesized that the right testis serves a compensatory role and increases in size when the left one is defective, and further suggested that testes asymmetry may be a reliable indicator of individual body conditions. In this paper, we tested the compensation hypothesis in the Guenther’s frog, Hylarana guentheri.From 60 sampled males, we found that there was a signifi cant directional asymmetry in testes mass, with the left testis size being significantly correlated with relative testes asymmetry, providing evidence that the right testis had a compensatory function. However, testes mass and asymmetry were not correlated with body condition .ence, we found no evidence that testes asymmetry in the Guenther’s frog ref lected male condition, and male age was also not not related to testes mass or asy mmetry.