The objective of this study was to determine the effect of (HOCl) treatment on the infectivity of hepatitis A virus (HAV). Prodromal chimpanzee feces, shown to induce hepatitis in marmosets (Saginus sp.), was clarified (JA 20/8K/30 min/5C), the virus precipitated with 7% PEG 6000, harvested (JA 20/8K/30 min/5C) and resuspended. The suspensions were layered onto 5-30% linear surcrose gradients, centrifuged (SW27/25K/3 hrs/5C) and the fractions containing HAV were pooled, dialyzed and ampulized. A 1:500,000 dilution of this preparation induced hepatitis in 2/4 and seroconversion in 2/4 marmosets. A 1:50 dilution of this preparation that routinely produced hepatitis in 100% of the marmosets inoculated served as inoculum for subsequent experiments.