BACKGROUND The cause of sporadic ALS is currently unknown. Despite evidence for a role for genetics, no common genetic variants have been unequivocally linked to sporadic ALS. We sought to identify genetic variants associated with an increased or decreased risk for developing ALS in a cohort of American sporadic cases. METHODS We undertook a genome-wide association study using publicly available samples from 276 patients with sporadic ALS and 271 neurologically normal controls. 555 352 unique SNPs were assayed in each sample using the Illumina Infinium II HumanHap550 SNP chip. FINDINGS More than 300 million genotypes were produced in 547 participants. These raw genotype data are freely available on the internet and represent the first publicly accessible SNP data for ALS cases. 34 SNPs with a p value less than 0.0001 (two degrees of freedom) were found, although none of these reached significance after Bonferroni correction. INTERPRETATION We generated publicly available genotype data for sporadic ALS patients and controls. No single locus was definitively associated with increased risk of developing disease, although potentially associated candidate SNPs were identified.