A study was carried out in 14 cancer patients to assess the relative bioavailability of two oral formulations of navelbine. A single 130 mg oral dose of the drug was given according to a randomized two-way crossover design as two capsules: one contained the drug in powder (formulation A, reference); another contained the drug in solution (formulation B). A 7 d washout period separated each dose. Navelbine was rapidly absorbed after administration of either formulation and exhibited a biphasic concentration decay pattern. The peak plasma level was reached within 2 h of administration in most patients. Formulation B resulted in better navelbine absorption with respect to peak plasma concentration (Cmax) and area under the plasma concentration-time curves (AUC) than did formulation A as ascertained by analysis of variance (ANOVA). The relative bioavailabilities (solution versus powder) were, respectively, 286.0% and 268.0% as estimated from experimental (0-72 h) and extrapolated (0-infinity) AUC.