The natural habitat of Pseudomonas species is soil, water, and plants.1 With the exception of the obligately parasitic mammalian species, P. mallei, pseudomonads are free-living, ubiquitous bacteria. P. aeruginosa is, of course, the species most often found in clinical samples. Low doses of P. pseudomallei, causing chronic melioidosis in mice, provided a 40-fold increase in immunity against respiratory reinfection. All serotests for P. pseudomallei cross react with P. mallei and some also with Yersinia pestis. Antimicrobial susceptibilities of unusual Pseudomonas spp. show inter- and intraspecies variations which call for the testing of every significant human strain. In contrast to P. aeruginosa, many strains are susceptible to kanamycin, neomycin, tetracycline, the combination of trimethoprim-sulfamethoxazole, and also to sulfonamides. A. faecalis has probably been isolated quite frequently and from numerous human sources. Earlier reports of isolation, however, are by and large unsupported by evidence that would exclude Achromobacter spp.