The one-step growth curve was measured for bacteriophage PM2 in Pseudomonas BAL-31, grown in synthetic medium at 25°. All virus was completed and found inside the cell prior to release. The eclipse period was 35-37.5 min, the latent period 40-45 minutes, and the burst size 684 PFU/cell. Cellular DNA synthesis stopped soon after infection but cellular DNA remained stable and there was considerable, but reduced, synthesis of cellular RNA throughout the course of infection. The rate of DNA synthesis was much higher in the infected cell than in the control cell and this proved to be viral DNA, according to hybridization tests. Viral DNA continued to be synthesized up to the time of cell lysis, even though synthesis of infectious virus stopped long before this time. Hybridization tests were also used to demonstrate the synthesis of viral mRNA, which continued up to the time of cell lysis. © 1969.