The Lambert-Eaton myasthenic syndrome (LEMS) is often associated with carcinoma. The exact number of patients with tumor has been reported to be as high as 70%. Recent clinical experience suggests that the actual number of patients with tumor may be substantially lower. We combined data from the clinical experience of the neuromuscular services at West Virginia University and the University of Virginia to determine the rate of occurrence of cancer in this disorder. We identified 28 patients with LEMS, and 14 had cancer. There is a distinct trend for a lower tumor frequency over the past decade, which suggests that the clinical manifestations of the disease may be changing.