Thirty cases of juvenile myasthenia with at least 2 years' follow-up and one measurement of acetylcholine receptor antibody titer were evaluated. Symptoms were initially ocular in 15 (50%) cases; only one developed generalized disease and others remained ocular in 2-24 years' follow-up. Antibodies to acetylcholine receptor (AchRAb) were absent in 12/30 (40%) of all patients initially, but became positive in 5/28 (18%) on further testing in 1-5 years. Spontaneous remission was observed in 6 cases (20%) of whom one became seropositive, and late relapses after 5-11 years' remission were observed in 3 patients with ocular myasthenia, of whom only one developed AchRAbs. Our results show ocular JM has an exceptional tendency to remain confined to these muscles, and delaying the classification of the disease as AchRAb-negative for a few years and repeating serological tests is advisable in the follow-up. © 2005 Published by Elsevier B.V.