The vinca alkaloid modification product, vindesine, presents closely related molecular structure to vincristine. Although there are differences in capacity to bind tubulin dimer and inability to inhibit growth of several experimental tumors, there is a significant degree of overlap. In the clinical tests to date, vindesine has been used in treatment of children with relapse of acute lymphocytic leukemia considered to be resistant to vincristine. The study presented here was designed to assess the degree of overlap between vincristine and vindesine. The conclusion was reached that there is clinical cross-resistance.