To elucidate whether serum coenzyme Q10 levels are related with the risk for amyotrophic lateral sclerosis (ALS), we compared serum levels of coenzyme Q10 and the coenzyme Q10/cholesterol ratio, in 30 patients with ALS and 42 matched controls using a high performance liquid chromatography technique. The mean serum coenzyme Q10 levels and the coenzyme Q10/cholesterol ratio did not differ significantly between the 2 study groups. These values were not influenced by the clinical form (spinal vs. bulbar) of ALS, and they did not correlate with age, age at onset, and duration of the disease. These results suggest that serum coenzyme Q10 concentrations are unrelated with the risk for ALS.