Studies on bacterial whole cell protein profiles showed that members of the rRNA group II pseudomonads were distinct from other non-fluorescent and fluorescent pseudomonads, including Pseudomonas aeruginosa, the type species of the genus Pseudomonas. Strains of Ps. andropogonis, Ps. caryophylli, Ps. gladioli pv. gladioli, Ps. pickettii, Ps. pseudomallei and Ps. rubrisubalbicans showed uniform and distinct protein patterns, while strains of Ps. solanacearum and Ps. cepacia displayed differences within species. Numerical analysis of their protein profiles with GelManager and Taxan programs generated dendrograms comprising 16 clusters at 89% similarity. Each cluster included strains belonging to the same species with the exception of Ps. solanacearum, which fragmented into three clusters. Pseudomonas solanacearum showed different protein patterns correlating with different biovars and the two divisions of Cook et al. (1989), as well as the results of 16S rRNA gene sequencing. The whole cell protein profiles of a total of 83 strains belonging to 14 bacterial species were numerically analysed.