The aim of this study is the evaluation of the level of antiacetylcholine receptor antibodies in patients with different types of myasthenia (according to Osserman's classification) and establishing of correlation between the level of such antibodies and the clinical state of the patients. 63 patients with diagnosed myasthenia and 30 healthy controls without immunological diseases were evaluated. In all of them standard neurological examination was performed and the levels of antiacetylcholine receptor antibodies were measured. In 45 patients electrophysiological investigations were carried out. In 43 cases elevated levels of antiacetylcholine receptor antibodies were noted. In 20 patients the levels were within normal range. The level of antibodies showed correlation with the clinical type of myasthenia according to Osserman (the more severe was myasthenia, the higher was the level of antibodies). But the clinical state of the patient at the moment of examination did not show any clear correlation with the level of antibodies. Acetylcholine receptor antibodies measurement has significant diagnostic value in myasthenia. Nevertheless it should be interpreted with other diagnostic techniques.