During the 19 year period ending December 1984, 4840 strains of Gram-negative non-fermentative bacteria were submitted to the National Collection of Type Cultures for identification. Of these, 195 strains (4.0% of the total) were identified as Pseudomonas cepacia which demonstrates both that the species is regularly encountered in clinical material in the UK and that several laboratories have experienced difficulty in identifying the organism. The sources from which the 195 strains were isolated are reported and also the characteristics by which the species may be recognized. The clinical significance of Ps. cepacia is reviewed, and the resistance of this species to disinfectants and antimicrobial agents commonly used to treat pseudomonas infections is discussed to underline the necessity for the precise identification of Ps. cepacia.