Two cases of Lambert-Eaton syndrome are reported, one associated with a small cell lung carcinoma, the other without any etiology at the time of the study. None of these cases showed significant titers of calcium channel autoantibodies. The heterogeneity of the Lambert-Eaton syndrome and the responsibility of the autoantibodies detected by immunoprecipitation of the voltage-gated calcium channel in the occurrence of the neuromuscular block are discussed.