A physical map of the group A streptococcal bacteriophage A25 genome was constructed using data obtained from restriction enzyme digestion analysis of purified DNA. Phage A25 was 34.6 kb in size and was digested with several enzymes which generated the following number of fragments: AvaI (3), EcoRI (2), HindIII (4), HaeII (10), HindII (22), HpaI (11), and PvuII (8). Restriction enzymes BamH1, PstI, and SaI did not cleave phage A25 DNA. A physical map of the group C streptococcal phage C1 genome was also constructed. Phage C1 was 16.9 kb in size and was cleaved by the following enzymes to give the indicated number of fragments: EcoRI (8), HaeII (10), HaeII (4), HaeII (10), HindIII (5), HpaI (8), PvuII (3), and SalI (2). Restriction enzymes AvaI, AvaII, BamH1, EcoRV, HpaII, and PstI did not cleave phage C1 DNA.