A method is presented for the description of a heterogeneous cell population with respect to the volume and density of its cellular components, based on computer analysis of the cell-volume spectra of density-gradient fractions. Display programmes were developed to produce either a perspective plot or an isofrequency contour plot ("fingerprint") of the two-parameter data. The use of sequential density and velocity gradients permitted the separation and study of the properties of any subpopulation. We describe the results of an analysis of cellular heterogeneity in an ovarian carcinoma cell line and in 2 cases of ascites cells from human ovarian carcinoma. The proliferative state (labelling index) and growth potential (culture clonogenicity) of cells from one malignant ascites have been "mapped" in terms of density/volume parameters. The results are discussed in terms of their impact on the view of human ovarian carcinoma as a stem-cell system.