1. 1. The biochemical and energetic compositions of the somatic body components of seven species of asteroids, one ophiuroid, and four echinoids from the northern Gulf of Mexico (30-95 m depth) were ascertained. 2. 2. Levels of ash were high (68.5-90.8% dry wt) in all body-wall tissues, with the exception of the asteroid Echinaster modestus (51.6% dry wt). Levels of ash were low in the pyloric cecae (nutrient storage organ) of asteroids (4.6-30.8% dry wt). 3. 3. Levels of lipid (8.1-34.5% dry wt), soluble protein (15.9-28.7% dry wt), and insoluble protein (18.1-48.6%, dry wt) were high in the pyloric cecae of all asteroids, but generally low in ophiuroid and echinoid body-wall tissues. High protein levels (28.5-44.5% dry wt) in the body-wall of the asteroids Echinaster modestus and Anthenoides pierceisuggest it may play a role in nutrient storage. 4. 4. All somatic tissues contained low levels of carbohydrate (0.2-1.4% dry wt). 5. 5. Levels of energy in pyloric cecal tissues (12.99-26.05 kJ/g dry wt) were 4-8 times higher than in echinoderm body-wall tissues (2.92-11.91 kJ/g dry wt). 6. 6. The biochemical and energetic compositions of echinoderms from the northern Gulf of Mexico are similar to those of species from other latitudes and depths. © 1990.