BRIDGE, P. D.&HUDSON, L., 1989. Use of continuous flow microfluorimetry for DNA determinations in Penicillium. Continuous flow microfluorimetry has been used to characterize spore suspensions of fasciculate strains ofPenicillium.Fluorescent Feulgen staining combined with appropriate filters allows the measurement of conidial DNA content in samples of 10 000 conidia in 30 seconds. The results obtained for apparently closely related strains and single conidium isolates of the same strains showed significant differences which appear to correspond with phenotypic differences. Some implications of, and possible explanations for, this phenomenon are discussed.