We analyzed 49 patients with multiple myeloma (MM) using propidium iodide (PI) staining and flow cytometry to assess DNA content of MM cells in bone marrow. In 12 patients the presence or absence of DNA content aneuploidy could not be determined by analysis of single-parameter DNA histograms alone. Using forward light scatter measurement, resolution of ploidy was readily obtained in all but three cases. Assuming the DNA content of the low light scatter population to be diploid, we were able to classify 7 cases as hypodiploid and 39 as hyperdiploid or diploid. Hyperdiploid or diploid patients survived a median of 24 months and hypodiploid patients only 2.5 months. We conclude that multiparameter analysis of DNA content and light scatter provides easier analysis for the presence or absence of aneuploidy. Patients with DNA content hypodiploidy have a short survival.