Recent studies have suggested that thymus tissue of the calf may bear nicotinic acetylcholine receptors. The presence of similar receptors in thymus tissue of man could thereby serve as a source of antigen for the production of antibody to the acetylcholine receptor in patients with myasthenia gravis. In the present experiments, human thymus tissue was examined for the presence of acetylcholine receptor. Both [125I] alpha-bungarotoxin binding and antiserum to the human acetylcholine receptor were used in tests for acetylcholine receptor in thymus glands from normal individuals and from patients with myasthenia gravis. Neither normal nor myasthenic thymus tissue were found to possess the [125I] alpha-bungarotoxin binding or the antigenic properties of the acetylcholine receptor.