Mutations in the optineurin (OPTN) gene cause amyotrophic lateral sclerosis (ALS). We previously reported 3 types of OPTN mutation in Japanese ALS subjects. Here, to identify the OPTN mutations in individuals of different ethnicity, we screened 563 sporadic ALS (SALS) subjects and 124 familial ALS (FALS) subjects who were mainly Caucasian. We found a c. 964T>C synonymous variation in exon 8. However, we could not find the meaningful OPTN mutations. The results indicate that OPTN mutations causing ALS are rare, especially in mainly Caucasian ALS subjects.