Males and females show different patterns of cognitive impairment when blood alcohol concentrations (BACs) are high. To investigate whether gender differences persist at low BACs, cognitive impairment was tested in 21 participants (11 female, 10 male) using a brief computerized perceptual judgment task that provides error rate and response time data. Participants consumed a measured dose of alcohol (average peak BAC: females: 0.052 g/100 mL, males: 0.055 g/100 mL), and were tested at four time points spanning both the rising and falling limbs of the BAC curve, in addition to a prealcohol time point. Comparisons were made against performance of these same participants at equivalent time points in an alcohol-free control condition. Males and females displayed a trend toward slower responses and more errors, even when mildly intoxicated. These data indicate that cognitive function can be impaired at BACs that are below the legal limit for driving in most countries.