Salmonella choleraesuis was isolated in pure or mixed bacterial cultures from 153 swine necropsied between Jan 1, 1987 and Dec 31, 1990. Pneumonia was seen in 99 of 109 swine from which this bacterium was isolated in the absence of other pathogenic bacteria. Pneumonia was seen more frequently than hepatitis, splenomegaly, or colitis. Pleuropneumonia that was grossly indistinguishable from the pleuropneumonia associated with Actinobacillus pleuropneumoniae was seen in 29 of 99 swine from which S choleraesuis was the only bacterium isolated.