The results of a study, on the fishery and biology of dogtooth tuna, Gymnosarda unicolor (Ruppell), conducted at Minicoy during 1995 to 1999 are presented. The resource is exploited from around the reef areas during July-August or September for sustenance when the usual fishing activities like pole and line and trolling are suspended. The total catch in a season varied from 56 to 481 kg. The size ranged from 44 to 126 cm fork length with the modal group at 58 and 62 cm. The length-weight relationship was found to be Log W = -4.5337 + 2.77 Log L. Fish below 70 cm size was found to be immature.