We report the absence of superoxide dismutase (SOD-1) gene mutations in 30 patients with amyotrophic lateral sclerosis (ALS) including individuals with a confirmed family history of ALS (familial ALS/FALS), ALS with an unclear family history (UFALS) and sporadic ALS (SALS). Single strand conformation polymorphism (SSCP) and sequence analysis of the 5 SOD-1 gene exons were undertaken to improve the accuracy of the mutation detection. Our preliminary data appear to diverge from the results of studies by other groups using different populations. We discuss the possible reasons for this disparity and the apparent heterogeneous distribution of ALS with SOD-1 gene mutations among different ethnic groups.