Two types of pyocins were simultaneously found in Pseudomonas aeruginosa strains HCP2. According to their structures, they belonged to the types classified as R and F, respectively, and were named HCP2-R and HCP2-F. The sensitivity of 87 strains of P. aeruginosa of clinical origin to pyocins of strain HCP2 was compared in different types of tests. Results indicated that the use of the purified pyocins for the typing of P. aeruginosa provides data which are easier to control and interpret.