A patient with Lambert-Eaton myasthenic syndrome was clinically treated several times over a period of 9 months. During at least 3 weeks each time, the patient received prednisone, then underwent 9 plasmaphereses, and was given guanidine-hydrochloride (HCl) and 3,4-diaminopyridine (3,4-DAP). The muscle-power scoring, muscle function tests and the electrophysiological parameters showed a superiority of 3,4-DAP over the other pharmacological therapies. Good results were also obtained with plasmapheresis. Corticoid medication proved to be less effective. No improvement was seen with guanidine-HCl. For comparative judgement, two months after beginning the last therapy, the patient and the attending physician were questioned with regard to subjective therapeutic success. The answers largely match the objective results. Both favour 3,4-DAP. In contrast to the patient's opinion, the physician sees a distinct effect of plasmapheresis. All in all, the administration of 3,4-DAP may be seen as an effective and acceptable therapy in Lambert-Eaton myasthenic syndrome.