the origin of amyotrophic lateral sclerosis (als) remains unknown, although it seems to be multifactorial. the role of environmental factors has been frequently investigated and suspicion of its influence can be obtained when clusters of a rare disease are described. objective: to describe conjugal cases of als in brazil. method: we describe 2 couples in which both spouses were affected by als. both couples had lived in southeast brazil and were married for at least 20 years. results: there was a great variability in clinical presentation of als in our patients. in both couples the interval between disease onsets was short. no precise environmental factors could be identified at the origin of these conjugal cases. conclusion: the occurrence of als in couples living in the same area may be epidemiologically important, but we cannot exclude that cases may be due to a chance association.