The characteristics of 'Clostridium diffiile' strains recovered from patients in Ontario healthcare facilities were studied. ' Clostridium difficile' toxin ELISA positive fecal samples were collected from 21 Ontario healthcare facilities between March 2005 and April 2006. Positive isolates were obtained from 1080/1152 (94%) samples, and were PCR-ribotyped. Presence of 'C. difficile' toxins A, B and CDT ribotypes was determined. Antimicrobial susceptibility was tested with the antimicrobials metronidazole, vancomycin, levofloxacin and clindamycin using E-tests. Presence of 'tcdC' gene deletion and toxinotyping was performed on all 39 distinct ribotypes. One ribotype accounted for 25% of isolates, while ribotype 027/NAP1, an internationally recognized outbreak strain, accounted for 19% of isolates. CDT prevalence was unexpectedly high (34.8%), and 6 ribotypes had a deletion in the 'tcdC' gene. One isolate showed reproducible metronidazole resistance but resistance was eventually lost during serial passage culture. 1080, 1076 and 0 isolates were susceptible to vancomycin, clindamycin and levofloxacin respectively.