The effect of anti-neoplastic agents on the growth of microorganisms was studied in vitro using aerobic BacT/Alert standard and FAN bottles as the culture media. A 50% longer incubation period to detect microbial growth compared to the control group was interpreted as growth inhibition. Idarubicin inhibited the growth of all of the five gram-positive cocci, one of five gram-negative rods and one of three yeast strains studied in the standard bottles but not in the FAN bottles. Candida glabrata was the most sensitive strain. Its growth was inhibited in the presence of idarubicin at a concentration of 1 micromol/l.