Rolipram-induced apoptosis in CLL cells is detectable by Hoechst 33342 flow cytometry. Cells were cultured for 72 hours in media (1), 1 μmol/L rolipram (2), 40 μmol/L forskolin (3), or a combination of the two drugs. The abcissa reflects forward light scatter and the ordinate Hoechst 33342 fluorescence. Apoptotic cells are characterized by reduced forward light scatter and increased Hoechst 33342 fluorescence.