In an attempt to gain more in-vitro-knowledge on the process of adsorption between bacteriophage and susceptible host cells, empty cell membranes of E. coli B have been prepared by enzymatic digestion procedures and exposed to the phages of the T-series. It was found, that T 2, T 4 and T 6 are adsorbed specifically by isolated membranes. The kinetics of adsorption on membranes resemble in every detail those obtained with living bacteria. Electron micrographs and observations with the phase contrast microscope give strong evidence of drastic alterations occurring to both phage particle (T 2) and membrane on which it is adsorbed. Enzymatic activities on the part of the phage paralleling those encountered with viruses of the Mumps-NDV-Influenza Group may be involved. But the process of adsorption becomes irreversible with T 2 and membranes. It is hoped to have a system at hand allowing further study under simplified conditions of the mechanism of penetration of certain types of phages through the intact cell wall of their host.