Disseminated blastomycosis was diagnosed in a 27-yr-old woman during her twenty-eighth week of pregnancy. Her skin lesions resolved promptly on treatment with amphotericin B. At full-term delivery when the mother had already received 1,536 mg of amphotericin B, the infant was normal and the placenta showed no evidence of blastomycotic infection. After administration of 16 mg of amphotericin B over 140 min, at delivery the concentrations of amphotericin B in serum of blood samples from the mother and the cord were 0.32 and 0.12 micrograms/ml, respectively. The published experience with systemic mycoses and amphotericin B treatment in pregnant women is reviewed. There is no evidence of teratogenesis or persistent toxic side effects in infants delivered from mothers treated with this drug during pregnancy.