Bacteriophage phi W-14 is sensitive to osmotic shock. It contain sufficient free putrescine, 2-hydroxyputrescine and spermidine to neutralize about 15% of the DNA phosphates. The alpha-putrescinylthymine residues of the DNA could neutralize a further 25% of the phosphates. Label is transferred from ornithine to the alpha-putrescinyl residues of phi W-14 DNA. The rates of polyamine synthesis in Pseudomonas acidovorans are increased by phi W-14 infection.