Frontal Assessment Battery (FAB) is short neuropsychological battery for the bed side screening of frontal lobe function. Several studies have indicated that frontal lobe dysfunction is the main neuropsychological feature in Amyotrophic lateral sclerosis (ALS). We examined frontal lobe function in patients with ALS and in age-matched normal subjects by using the FAB. We examined 24 patients with sporadic ALS aged 66.0 +/- 10.1 years, with a mean disease duration of 2.0 +/- 0.7 years, a Mini-Mental State Examination score of > or = 24, a normal self-rating depression score, no dyspnea, and no or only slight disturbances in speech, cutting food, and handling utensils on the ALS Functional Rating Scale. Total FAB score, similarity score, and lexical fluency score were significantly lower in ALS patients. Total FAB score did not correlate with age, disease duration, ALS Functional Rating Scale, spirometry, or blood gas analyses. These results suggest frontal lobe dysfunction in ALS patients.