To the Editor:— Dr. Krugman and his associates deserve congratulations for their study of infectious hepatitis reported inThe Journal, Oct. 15, 1960. However, their statement concerning the optional dose of gamma globulin for the prevention of infectious hepatitis merits discussion. The authors think that 0.01 ml. is perhaps "adequate for the prevention of the mild childhood disease but inadequate for the adult type." On the basis of their experience, and because they could find no published evidence, they believe this dose is not enough for adults. As to their experience with adults in Willowbrook, it was very small, and one may ask if the attendants inoculated and uninoculated with 0.01 ml. were equally exposed to hepatitis. In 1953-1954 the New York State Department of Health studied the families of 2,000 reported patients with infectious hepatitis. Some of the families were inoculated with gamma globulin; others, for various reasons, were