To examine physical proximity as a risk factor for the nosocomial acquisition of Clostridium difficile-associated diarrhea (CDAD) and of antibiotic-associated diarrhea (AAD), we assessed a retrospective cohort of 2859 patients admitted to a community hospital from 1 March 1987 through 31 August 1987. Of these patients, 68 had nosocomial CDAD and 54 had nosocomial AAD. In multivariate analysis,...