Colonization of sputum by Pseudomonas cepacia has been associated with progressive respiratory deterioration and a worsening prognosis for some cystic fibrosis patients. After laboratory methods were changed and a selective medium introduced, P. cepacia was isolated from the sputa of 16 out of 82 patients with cystic fibrosis attending this hospital: a prevalence rate of 20%. P. cepacia was found in the first sputum examined of 12 patients after the new methods were introduced, indicating that colonization was not necessarily a recent event. All isolates were satisfactorily identified using conventional media but half were identified with only a low level of confidence using the API 20NE kit. Further studies using adequate laboratory methods are required to determine the prevalence and significance of this organism in Australia.