THE widespread use of antimicrobial agents may have completely resolved many perplexing problems in the field of infectious diseases but it has also created many new and even more perplexing ones. Among these are the various untoward effects, which have been increasing steadily; some are directly toxic, some are allergic, and others are related to the biologic activities of the chemotherapeutic substances. The reasons for an increased prevalence of undesirable sequelae to chemotherapy are mainly three: the increase in the number of antimicrobial agents, each of which may produce such reactions; the increase in the number of people treated so . . .