Hepatic encephalopathy (HE) is an increasingly prevalent and debilitating condition that occurs in functional hepatic insufficiency. It is marked by fluctuating neuropsychiatric and cognitive impairment, which can be severe and life threatening. Hepatic encephalopathy is a diagnosis of exclusion; thus, it is challenging to diagnose definitively and to investigate in clinical trials. High response rates in the placebo arms of well-conducted studies demonstrate that the most effective treatment for HE is the correction of known precipitating triggers. However, pharmacological therapies may also be helpful. Although the precise pathogenesis remains unknown, bacterially derived neurotoxins from enteric flora likely play an important role. Based on this hypothesis and on accumulating clinical experience documented in randomized trials, oral antibiotics have emerged as an important treatment adjunct. This article addresses the qualities of an ideal antibiotic and reviews the literature on 4 antibiotics used to treat HE: neomycin, metronidazole, vancomycin, and rifaximin, with the most promising of these drugs appearing to be rifaximin. Unfortunately, most studies of the treatment of HE are difficult to interpret due to small sample sizes, methodological flaws, vulnerability to bias, and the intrinsic challenges of studying HE. Many studies have erroneously concluded that treatments are equivalent simply because no significant difference between treatment arms was detected. Consequently, the literature generally lacks definitive data from large, randomized, placebo-controlled trials. Nevertheless, the data suggest that minimally absorbed antibiotics are emerging as a safe and effective approach for the treatment of HE.