Reveromycin B is a spiroketal bacterial metabolite originally isolated from Streptomyces. It inhibits EGF-induced mitogenic activity in Balb/MK cells (IC50 = 6 ug/ml) and exhibits pH-dependent antifungal activity against C. albicans (MICs = 15.6 and >500 ug/ml at pH 3.0 and 7.4, respectively). Unlike reveromycin A and reveromycin C , reveromycin B does not inhibit proliferation of KB and K562 cells.