The biology of the roudi escolar, Promethichthys prometheus, from the Canary Islands was studied. Specimens 38.3-78.9 cm in total length were captured from August 1992 to December 1993 around the islands. Male: female sex-ratio was 1:1.96. The spawning season extended from April to September with most gonadal activity in June-July. Size at first maturity was 51.9 cm for males and 52.9 cm for females. Weight grew allometrically with size. Fish from age 3 to 10 years were found. The von Bertalanffy growth parameters were L_∞= 90.1 cm and k= 0.17 yr^-1. The food consisted primarily of bony fishes, followed by cephalopods and crustaceans.