Kinetic changes induced by dianhydrogalactitol (DAG) [an antineoplastic drug] in cultured 9L rat brain tumor cells were studied using conventional autoradiography and flow cytometry. Cell cycle parameters for the untreated cell line were: G1, 8.5 h; S, 8.2 h; G, 3.2 h; M, 0.5 h; and cell cycle time, 19.5-20 h. Treatment with 5 .mu.g/ml of DAG, which caused 89.8% cell kill as measured by the colony-forming efficiency assay, resulted in the following effects: undisturbed progression of G2 cells toward mitosis, disturbed progression of the cells in the S-G2 boundary, extreme prolongation of DNA synthesis time and temporary accumulation in G2 phase of cells that were in G1 or S phase at the time of treatment.