The current use of metronidazole as an anti-amoebic agent causes significant side-effects. The purpose of this study was to identify alternative compounds with which to treat amoebiasis.We tested the effects of cyclopropyl (CPC) and cyclobutyl (CBC) carbinols on the survival of Entamoeba histolytica trophozoites and on the enzymatic activities of E. histolytica alcohol dehydrogenase 2 (EhADH2), a crucial enzyme in the amoebic fermentation pathway.At 72 h, the estimated 50% inhibitory concentrations of CPC and CBC were 38.9 and 11.2 microM, respectively. The EhADH2 alcohol and aldehyde dehydrogenase activities were inhibited by 1.82 microM CPC and 0.89 microM CBC in vitro.CPC and CBC are expected to be non-toxic to humans at the concentrations required to eliminate E. histolytica trophozoites. Similarities between EhADH2 and the Giardia lamblia AdhE enzyme indicate that CPC and CBC could be effective drugs for treatment of both amoebiasis and giardiasis.