Now that flow cytometric DNA analysis is becoming an established procedure, many samples that are being received from various hospitals cannot all be analyzed within a day. Therefore, samples must be stored for subsequent analysis in a flow system. To determine a proper temperature for storage by freezing, samples of the same material were stored for 2 weeks at 5 degrees C, -80 degrees C, and -195 degrees C. Measurement and analysis at the end of this period revealed no major differences among the subsequent histograms of these samples. Thus, it seems that a flow cytometric DNA analysis can be made of frozen samples for diagnostic and prognostic evaluations.