['Pathological skeletal muscle weakness is an axial clinical symptom of myasthenia (MG). Diminished respiratory muscular force can be manifested by decreased peak expiratory flow (PEF) value.', 'Patients aged 13-77 years were studied at which according to Osserman classification ocular form (the type I) or generalized form (the type II) was diagnosed (n = 68). PEF and FVC values such as % of predicted value (PV) obtained in "flow-volume" measure were analysed. The trunk and extremities muscles force was estimated according to Besinger.', 'Weakness of lower extremities muscles was found at all examined subjects. Positive result of trunk muscle test was found in 69% of patients with type I and 89% with type II. In type II upper extremities muscles (UEM) weakness was observed more often than in type I (74% subjects vs. 31%). In both types of MG the mean value of PEF was lower in patients with UEM weakness and amounted 89.5% vs. 112.4% in type I and 87.4% vs. 100.4% in type II. In type I the mean value of FVC was lower in patients with UEM weakness than in patients without symptoms (83.7% vs. 106.2%), with trunk muscles weakness (93.8% vs. 111.7%) and in patients with decreased muscles force up to 15% (87.5% vs. 106.7%). In this type of MG decreased value of FVC < 80% PV was observed in 50% of patients with UEM weakness and in 40% of patients with decreased muscles force up to 15%, but at none of subjects without symptoms in above tests.'] Do [ The comparison of selected spirometric parameters with functional muscles exercise evaluation in patients with myasthenia ]?