Vincristine has been a key drug in the treatment of acute lymphoblastic leukemia for almost three decades [1], but our knowledge of its pharmacokinetics is still limited due to a lack of sufficiently sensitive and specific assays for the measurement of vincristine in biological fluids [2]. Thus, while neurotoxic adverse effects of vincristine have been extensively reported [3–11], little information is available about possible pharmacokinetic-pharmacodynamic relationships.