Rats chronically received -bungarotoxin which caused a reduction of nicotinic acetylcholine receptors and weakness, especially of lip muscles. It was found that diazepam (0.75 – 2mg kg^–1, s.c), after a 15 min period of excitation and increased lip weakness, caused sedation and some improvement of the lip. Even after 5mg kg^–1 diazepam, muscle function was not markedly affected and breathing appeared normal. It is concluded that sedation in rats by diazepam does not entail aggravation of the muscle weakness caused by a partial neuromuscular block.