A mixture of Rhinomonas (red algae) and Isochrysis (green algae) was analyzed using a Coulter EPICS ELITE flow cytometer. Fluorescence resulting from excitation with the argon (488 nm) laser was collected using a 575 nm BP filter (PMT3) and a 675 nm BP filter (PMT5). Using autofluorescence, the two populations of algae can easily be distinguished.