The DNA of phi FR114, a temperate phage of the thermophilic actinomycete Faenia rectivirgula, was hybridized with the genomes of 11 different phages of Faenia and Saccharopolyspora. This revealed several regions (modules) within the phi FR114 DNA which were distributed independently among the genomes of the other phages. The genome of the lytic phage 121, originally described for Sap. erythraea, exhibited a similar modular organization. So far no functions of the possible modules are known.