Diaziquone (AZQ) is a benzoquinone derivative exhibiting significant effects against CNS tumors. This study investigates the pharmacokinetics of AZQ for three different durations of continuous iv infusions, over 20 mins, 4 hrs, and 6 hrs, in nine patients with CNS malignancies. Total AZQ doses varied from 10 to 20 mg. The average elimination half-life was 37.2 +/- 13.9 mins, the total clearance was 515 +/- 280 ml/min or 11.3 +/- 5.9 ml/min/kg, and the apparent volume of distribution by area was 26.5 +/- 14.7 L or 0.62 +/- 0.50 L/kg. Peak concentrations after the 20-min infusions (three patients) varied from 0.58 to 1.20 micrograms/ml, whereas concentrations during the 4-hr infusions (three patients) varied from 0.02 to 0.37 micrograms/ml, and during the 6-hr infusions (three patients) varied from 0.02 to 0.61 micrograms/ml. These results indicate that concentrations found to exhibit minimum inhibitory effects in in vitro cell studies are achievable during prolonged iv infusions of AZQ.