Strains of thermophilic campylobacters of human origin were examined for bacteriocine activity and for susceptibility to R-type pyocines of Pseudomonas aeruginosa. None of 50 strains inhibited the growth of any other strain, but 13 of 80 strains (16%) were sensitive to R-type pyocines. Absorption of one of the partially purified pyocine preparations with a sensitive strain resulted in the removal of pyocine activity and a decrease in viable count of the organism by 85%.