The growth characteristics and colonization potential of a transplantable melanoma administered to young (3 mo) and old (24 mo) C57BL/6 mice were investigated. After sc injection of B16-F10 melanoma cells, tumor growth was slower, and final tumor volume was less in the older mice. Furthermore, after iv injection of B16-F1 melanoma cells, the number of pulmonary colonies was also less, and the survival was greater in the older mice. These findings indicate an age advantage in this experimental tumor model that may be attributed to either physical or immunologic factors.