The pharmacokinetics of cytarabine (ara-C) were determined in 265 patients with acute myeloid leukemia (AML) receiving ara-C (200 mg/m² per day for 7 days as a continuous infusion) and daunorubicin during induction therapy. The mean (standard deviation) ara-C concentration at steady-state (Css) and systemic clearance (Cl) were 0.30 (0.13) M and 134 (71) l/h per m² respectively. Males had a significantly faster ara-C Cl (139 vs 131 l/h per m²,P=0.025) than females. Significant correlations were noted between ara-C Cl and the pretreatment, peripheral white blood cell count (P=0.005) and pretreatment blast count (P=0.020). No significant differences in ara-C Css or Cl were noted in patients achieving complete remission compared with those failing therapy (P=0.315,P=0.344, respectively). No significant correlations were observed between ara-C pharmacokinetic parameters and several indices of patient toxicity. Our findings indicate that variability in ara-C disposition in plasma at this dosage level does not correlate with remission status or toxicity in patients with AML receiving initial induction therapy with ara-C and daunorubicin.