Two male infants with neonatal myasthenia gravis are described. The serum of one patient and his myasthenic mother had no neuromuscular blocking activity or antinuclear globulin. Striation binding globulin was positive in the serum of the mother, but not the infant. Eighty two collected patients are reviewed. Incidence was 12% of babies born to myasthenic mothers. Onset was within 72 hours of birth. Mean duration was 18 days and maximum was 47 days. Nine patients died, with a mean duration of 6 days and a maximum of 21 days. The remaining patients recovered without recurrence, except for recurrence at 2 years in one patient. Manifestations were feeding difficulty (87%), generalized weakness (69%), respiratory difficulty (65%), feeble cry (60%), and facial weakness (54%), including ptosis (15%). Pharmacologic tests with neostigmine or edrophonium were positive in 86%. Management consisted of anticholinesterase medication in 81% for a mean of 21 days and general care, particularly respiratory care. The mothers all had generalized myasthenia gravis. Four mothers did not receive anticholinesterase medication and nine had undergone thymectomy. Eleven mothers subsequently had a second affected child, and five mothers had a normal child. There was no relation of neonatal myasthenia to striation binding or antinuclear globulin in serum of mother or infant.