Fifty-six phages designated the U-series and 34 phages designated the Ph-series were carefully examined. The spectrum of activity was established for 183 strains of Staphylococcus epidermidis from different countries and for 258 strains of Staphylococcus aureus. All 90 phages were active against strains of both species, but some differences in sensitivity were noted. Sixteen of the 90 phages were selected for phage typing of S. epidermidis. With use of a routine test dilution of phage (the highest dilution that yields confluent lysis of the propagation strain), 71.6% of 183 coagulase-negative staphylococci tested were sensitive to the phages; 42 phage patterns were observed. The results indicate that phage typing of S. epidermidis can be recommended for epidemiological and ecological purposes.