Abstract Amphotericin B and some of the imidazole drugs have been shown to suppress certain neutrophil and lymphocyte functions both in vitro and in vivo. We present here the in vitro effects of: amorolfin, a morpholine derivative; the imidazoles clotrimazole and ketoconazole; the N-substituted imidazole bifonazole and a triazole (ICE 195, 739), on neutrophil and lymphocyte function. All of these drugs inhibited neutrophil random migration, chemotaxis and hexose monophosphate shunt activity. The effects of the drugs on neutrophil adherence, deoxyglucose transport and beta-glucuronidase release were variable while lysozyme release was unaffected. Natural Killer cell cytoxicity was depressed by all drugs tested except for amorolfin. Mitogen-induced lymphocyte blastogenesis was suppressed by all antifungal drugs tested. Similar results were obtained using the mitogens phytohaemagglutinin, concanavalin A and pokeweed mitogen. The mechanism of action of these drugs on these cell functions remains unknown, there may be a correlation between their effects on fungi and their effects on leukocytes. Clearance of systematic fungal infection is heavily dependent on integrity of the cellular immune system and it is clearly undesirable that antifungal drugs have immunosuppressive properties. Further studies are required to determine the in vivo and clinical relevance of our observations.