The chemical structure of the ethanol soluble (ES) and ethanol insoluble (EI) antigens isolated from Trichinella spiralis larvae was determined. The ES antigen was found to be a glycoprotein averaging 75% protein and 15% carbohydrate. The polysaccharide consisted entirely of glucose units. The EI antigen, on the other hand, was found to be a nucleoprotein averaging 60% nucleic acid and 14% protein. The nucleic acid portion analyzed to be deoxyribonucleic acid. Studies on the enzymatic breakdown of the antigenic substances inferred that the protein portion of each antigen was needed for activity in complement fixation tests.