The toxicological study conducted revealed high concentrations of hydrocarbons and highly toxic heavy metals in the liver and subcutaneous fat of the Caspian seal. The increased toxicant level in the fat, as compared to the liver, pointed to the disorder of organism purification processes, leading to chronic polytoxicosis and disorders of the histological structure of the internals. The studies of the morphofunctional state of the stomach of the Caspian pinnipeds revealed the following disorders: hemorrhages, edemata and necrosis of the mucous membrane, and replacement of glandular tissue with the connective tissue. The study of the small intestine of the seals identified the symptoms of catarrhal desquamatory enteritis. Epithelium dystrophy and desquamation were noted, in particular at the tops of the villi. Different types of colitis (acute, ulcerative, chronic) were found in the large intestine of the seals. Dystrophic and necrotic changes of hepatocytes were identified in the liver tissue, which pointed to the liver cell failure. The nature and extent of pathological changes in the internals and tissues of the studied animals point to the functional depression of the digestive system.