The goal of this project was to compare the kinetics of chlorine inactivation of a naturally-shed virus and its tissue culture grown counterpart. Since inactivation studies require purified preparation possessing high infectivity titer and low chlorine demand a major part of this project was devoted to elucidate the best scheme of obtaining material with the necessary criteria. The scheme found most satisfactory was a combination of Freon 113 extraction, zonal sucrose gradient contrifugation (T1-15 rotor, 25,000 rpm for 3 hours) and pelletization (SW 27 rotor, 27,000 rpm for 3 hours). Using this scheme purified virus preparations derived from naturally shed or tissue culture source were tested for their susceptibility to chlorine inactivation. Preliminary results show that for their susceptibility to chlorine inactivation. Preliminary results show that the rate of chlorine inactivation differs with virus derived from fecal material (naturally shed) and that derived from tissue culture. The rate of inactivation indicates that the tissue culture derived virus is more susceptible to chlorine inactivation as compared to naturally shed virus.