Patients with the frontal variant of frontotemporal dementia (fv-FTD) exhibit deficits of executive functions. However, no single executive function task that might be used to detect the executive function deficits in fv-FTD patients has been established as yet. The frontal assessment battery (FAB) devised by Dubois et al. (2000) has been reported to be a quick and simple bedside screening test that is sensitive for differentiating between FTD and Alzheimer's disease (AD). The present study was conducted with the aim of ascertaining the reliability and validity of the Japanese version of the FAB among Japanese patients with fv-FTD. The Japanese version of FAB was given to patients with mild fv-FTD (n = 18) and those with AD (n = 18). The test-retest reliability was evaluated after a 3-week interval by the same interviewer. Data from the Wisconsin Card Sorting Test (Keio version: KWCST) were also collected to ascertain the validity of the FAB. The Japanese version of the FAB exhibited good internal reliability (Cronbach's alpha: 0.70, 95% confidence interval [CI] = 0.50-0.84) and good test-retest reliability (intraclass correlation coefficient: 0.89, 95%CI = 0.77-0.95). Significant correlations were observed between the total FAB score and the category achieved (r = 0.454, P < 0.05) and number of perseveration errors (number of errors that were perseverations; r = 0.719, P < 0.01) in the KWCST. A cut-off of 10 for the total FAB score yielded the highest sensitivity (85%) and specificity (92%) for discriminating between patients with fv-FTD and AD with the highest positive likelihood (12.0, 95%CI = 2.6-55.4). The Japanese version of the FAB offers promise as an easy and quick bedside screening test to distinguish fv-FTD from AD.