Mutants of Bacillus subtilis 168 were isolated which allow adsorption but not infection by bacteriophage SPP1. The adsorbed phages can be subsequently recovered in active form. From ten other bacteriophages tested, only the SPP1-related phages 41c, 22a, p15 and SF6 failed to plate on the mutant cells. The mutation responsible for this behaviour (pha-2) was mapped by PBS1 transduction, showing 95% cotransduction with ald-1.