A multicentre follow-up study of 1152 patients with myasthenia gravis in Italy. A multicentre retrospective study was carried out on the characteristics and course of myasthenia gravis (MG) in Italy. Data from 1152 patients, fairly representative of the myasthenic population seeking medical advice, were analysed for diagnostic criteria, clinical aspects and therapeutic approaches. Mean follow-up was 4.9 years. The disease was correctly diagnosed within 2 years of the onset in 80% of cases. Onset of symptoms peaked in the second and third decade in females and fell between 20 and 59 years in males. At first observation 87% of the patients had generalized MG. Maximal worsening was observed within 3 years in 77% of patients. At the last follow-up, 35% of cases were symptom-free (pharmacological remission 24%, remission without treatment 11%). The more severe the disease at the first observation and at the maximal worsening of symptoms, the lower was the proportion of remissions. Steroids were given in 54% and immunosuppressants in 18%. Thymectomy was performed in 72%, mostly in women, younger than age 40, and with generalized MG. Thymectomy seemed to improve the course of the disease, mostly in patients operated on shortly after diagnosis and those with generalized mild-to-moderate disease and with a normally involuted thymus. MG was lethal in 4% of patients, principally men, older than 40, in grade 3 or worse at first observation, with a short history of disease, and with thymona. 