The in-vivo activity of amphotericin B and itraconazole against a clinical isolate of Aspergillus terreus was determined in a murine model of disseminated aspergillosis. MICs of amphotericin B and itraconazole for the strain, determined by an NCCLSbased technique, were 2 ìg=ml and 1 ìg=ml, respectively. Mice infected intravenously were treated with either itraconazole (50 or 100 mg=kg=day) or amphotericin B 4.5 mg=kg=day for 10 days. Treatment with both doses of itraconazole signi®cantly prolonged the survival rates compared with those for untreated mice. In comparison, mortality rate and median survival time were identical for mice treated with amphotericin B and for mice given no therapy, indicating that the strain was highly resistant to amphotericin B in this model. Analysis of sterol composition showed that the major sterol was ergosterol. This suggests that amphotericin B resistance was not related to a modi®ed sterol pro®le.