A method based on staining condition and volume of culture broth for the rapid estimation of the level of intracellular lipids in Acremonium chrysogenum using Oil red O was developed. Lipids in A. chrysogenum were strongly stained by the modified Oil red O after treatment for 10 min at 75A degrees C. The results of the study indicated that the Oil red O staining method developed here is useful for the quantification of 0.1-5 mg ml(-1) of lipids in A. chrysogenum.