A collection of bacterial isolates were typed using the Ribo-Printer Microbial Characterization System (Qualicon, Wilmington, DE, USA), an automated ribotyping system, and pulsed-field gel electrophoresis (PFGE). Grouping patterns, discrimination, and typeability were compared. The collection consisted of 411 isolates of bacteria from 32 medical centers. The isolates included a total of 18 species (both Gram-positive and Gram-negative), covering the range of concern to a laboratory performing epidemiological investigations. The patterns of groups obtained by both typing systems were similar for all species examined. Ribotyping provided less discrimination than PFGE, especially for Serratia marcescens, and Pseudomonas aeruginosa. All strains were typed by the Ribo-Printer, but 2.75% were not typeable by PFGE. The Ribo-Printer has proven to be a valuable primary typing method for a high-volume laboratory, even for those species for which it provides a lesser degree of discrimination than PFGE.