The pharyngeal flora of a group of ambulatory alcoholic patients was studied and compared with the pharyngeal flora of a control group. Sixty-eight patients were studied, 34 alcoholics and 28 controls. Of the alcoholic patients, 59% had Gram-negative bacilli in their pharyngeal flora, while 14% of the control group had the same organisms. There were no differences in Gram-positive cocci colonization between the groups. Klebsiella pneumoniae was the most frequent isolate (40%) and the Klebsiella-Enterobacter group accounted for 76% of the isolates. Colonization rates of greater than 10 colony forming units/ml were found in 43% of the alcoholic patients. The high prevalence and higher colonization rates of Gram-negative bacilli in alcoholic patients might explain the higher incidence of Gram-negative bacillary pneumonia among alcoholics.