The analysis, by slab gel electrophoresis, of internucleosomal DNA cleavage or laddering, characteristic of apoptosis in many cell systems, is labour intensive, difficult to automate and at best only semi-quantitative. In this report we show that CE, using dilute solutions of hydroxyethylcellulose as a replaceable sieving matrix, can be applied to the relatively rapid analysis of DNA laddering in whole digests of apoptotic rat thymocytes. Also, using the sensitivity of laser-induced fluorescence detection and the highly sensitive nuclei acid stain YO-PRO-1, the CE method reported here can use 1000-2000 fold fewer cells than needed for traditional slab gel methods.