Pseudomonas sp. PhCN strain, which has the potential to utilize phenol and cyanide as a sole carbon and nitrogen source, was isolated. A comparison of the effect of cyanide on phenol degradation and vice versa by strain PhCN showed that the degradation time was significantly delayed by an increase in either phenol or cyanide concentration, and the greatest activities were obtained in basal medium containing a low concentration of cyanide and phenol. This strain contained two plasmids of approximately 120 kb (pPhCN-1) and 110 kb (pPhCN-2). Plasmid curing experiments produced a plasmid-free strain as well as strains containing either the 120- or the 110 kb plasmid. The strains were tested for their ability to utilize phenol and KCN. The results demonstrated that the ability to utilize phenol was encoded by the 120 kb plasmid, whereas the ability to utilize cyanide appeared to be encoded by the chromosome.