Sera from 627 students entering Colleges of Education between 1969 and 1972 were tested for hepatitis B surface antigen and antibody. One was found positive for antigen, none for antibody. Six for 15 positive Hepanosticon results and two positive Hepatest results occurred in sera which also gave positive heterophil antibody tests indicative of current or recent EB virus infection. One of these six sera was still positive in the Hepanosticon test after one absorption, and one of two Hepatests gave no positive reaction with the control cells. Eleven of 14 sera from cases of infectious mononucleosis gave positive Hepanosticon results and two were still positive after one absorption. Seven were positive in the Hepatest and only three of these were positive with the control cells. The control tests in the Hepanosticon and Hepatest do not clearly identify all false positives due to Paul Bunnell antibody. It is suggested that when a positive result in a passive haemagglutination test can be removed by absorption or if positive after absorption cannot be confirmed by other tests for hepatitis Bs antigen, the patient from whom the serum specimen was taken should be investigated for indications of current EB virus infection.