1,1-Difluoroethane (75-37-6) was evaluated for acute oral toxicity in 6 male Crl: CD BR rats administered doses of 200, 300, 450, 670, 1000, and 1500 mg/kg of by gavage. The use of controls was not specified. The observation period was 14 days post-treatment. No mortalities occurred. Clinical signs immediately after dosing in all rats included abdominal distension and lethargy. Clinical signs seen with 48 hours post-dosing included high carriage, wet and yellow stained perineums and diarrhea. Necropsy and a histopathological examination were not specified. The LD50 for 1,1-difluoroethane is greater than 1500 mg/kg, and was considered to be slightly toxic when administered as a single oral dose in rats.