Representative dot plots of BrdUrd content (log FITC fluorescence) vs. DNA content (propidium iodide fluorescence) of Jurkat cells at different post-labelling times. Jurkat tumour cells were labelled with BrdUrd for 30 min and then fixed after 8 h (A), 10 h (B), 12 h (C) and 16 h (D). A. Labelled cells have not yet entered the Sld compartment. B. Labelled cells start entering the Sld compartment. C. Considerable proportions of labelled cells are present both in the Sld and in the Slu compartment. D. Labelled cells are leaving the Slu compartment. The optimal time for measurement of cell kinetics in Jurkat cells with the proposed method appears to be 12 h.