The continuous search for new antimycotic drugs is a consequence of the broad use of immunosuppressive drugs and broad-spectrum antibiotics, high number of AIDS patients, and widespread dermatophyte infections. The concern with increased resistance due to widespread and prolonged antifungal treatment, particularly with azoles, is noteworthy. Our efforts were focused on medicagenic acid derivatives isolated from alfalfa and on semisynthetic ones. In general, these materials exhibited potent fungistatic effects against several plant pathogens and human dermatophytes. Furthermore, they were fungicidal against medically important yeasts, showing a most impressive activity against Cryptococcus neoformans, the minimal fungicidal concentration (MFC) value of the gluco derivative of medicagenic acid, compound G2, is 4 micrograms/ml. The mode of action as well as the structure-activity relationships of these compounds were studied. Compound G2, when applied topically, was effective in curing skin lesions of guinea pigs infected with the dermatophyte Trichophyton mentagrophytes and good skin tolerance to the drug was noted. Furthermore, it had a life-prolonging effect on mice infected with C. neoformans and recently, liposomes containing compound G2 were used efficiently as a drug delivery system in treatment of murine cryptococcosis and candidiosis.