Age in 96 individuals of a tropical frog Rana nigrovittata from Thailand was skeleto-chronologically investigated. Hematoxylinophilic lines interpreted as lines of arrested growth (LAGs) were observed clearly in the periosteal bone suggesting that this technique can be used to estimate the age of frogs from tropical Asia. The maximum age observed was nine years in males and six in females, but age structure did not differ significantly between the sexes. In the same age class, males were significantly larger than females.