To the Editor: In the January 10 issue, Perras et al. attempted to define the risk of acquiring non-A, non-B (NANB) viral hepatitis after direct contact with saliva from a patient with NANB viral hepatitis. The authors suggest that a lack of hepatitis-like illness or serum transaminase elevations in the exposed persons during the six-month period after exposure indicates that there is little risk of acquiring NANB hepatitis after such an exposure. However, 19 of the 23 persons in the NANB-hepatitis study received immune serum globulin (ISG) within two weeks after exposure. The efficacy of immune globulin prophylaxis in persons.