Providencia stuartii has emerged as a significant nosocomial urinary tract pathogen. An increase in the number of Providencia isolates from urine cultures prompted an investigation into the possibility of an outbreak due to this organism. A high proportion of patients studied had urinary devices. Four wards were screened at two time periods to ascertain the prevalence of Providencia stuartii in urine cultures. Biotype, serotype, antibiogram and plasmid content were determined for each Providencia isolate. Of 129 patients initially sampled 22.5% were found to harbor Providencia stuartii. Biotyping, serotyping and antibiograms indicated an epidemic strain was not present. Similar results were obtained when the wards were screened a second time, with 25.4% of urine cultures found to contain Providencia stuartii. By plasmid analysis the isolates could be grouped into one of ten profiles. A correlation could be made between urease activity and the presence of a large plasmid. No association however could be made between a particular plasmid profile and antibiogram. The data indicate that an epidemic strain of Providencia stuartii was not present. The source(s) of the endemic Providencia stuartii strains remain unknown.