From the college entrance health data of 50,000 male former students, the records of 45 who eventually died of Hodgkin's disease were compared with those of 180 surviving classmates with reference to certain indicator characteristics. Risk ratios of Hodgkin's disease tended to be lower for men who had experienced various common contagious diseases in childhood. This reduced incidence of clinical contagions may signify that: 1) Inadequate early challenge of immune mechanisms left subjects more susceptible to later Hodgkin's disease, whether or not it is of infectious origin; 2) heightened immune mechanisms that led to subclinical attacks of early contagious diseases promoted an autoimmune response that evolved as Hodgkin's disease; or 3) early childhood infections eliminated some subjects who otherwise would have attended college and ultimately developed adult-onset Hodgkin's disease. Also, Hodgkin's disease risk was higher for students who had reported early death of a parent, particularly from cancer. Moreover, the risk tended to be increased among collegians who were obese, heavy cigarette smokers, and coffee drinkers. None of these indicator characteristics was associated with 89 fatal lymphomas of other types that occurred in the same study population.