To the Editor: The use of pooled human serum gamma globulin (SGG) has long been accepted as prophylaxis for hepatitis A virus (HAV) infection. Dosage levels have been based empirically upon volumes of SGG per body weight, with no scientific criterion, except the apparent high frequency of success. Identification by immune electron microscopy1 of the agent responsible for hepatitis A infection and the successful in vivo cultivation of the virus in marmosets2,3 has led to the development of immunologic tests45678 for detection of hepatitis A antigen (HA Ag) and antibody (anti-HA). Miller et al.5 and, more recently, Frŏsner et . . .