Right and left adrenals were expressed as grams per kilogram body weight for 38 male and 31 female nutria. The average g/kg ratio is 0.627 for males, and 0.512 for females. There is a significant difference between right and left adrenals in both sexes (P < 0.001), the left adrenal being the larger in each sex. Body weights of one male and 3 females were recorded from 4 to 42 weeks of age. The sexual maturity of the females was reached at 5 months of age as indicated by vaginal opening.