Recently, levamisole combined with 5-FU was shown definitively to increase the survival of patients after surgery for colon cancer (9, 10). In the light of these findings the experimental and clinical findings with levamisole in the field of oncology are reviewed. The conclusion is reached that levamisole has proven activity, although its mechanism of action remains elusive. The progress that has been made in our understanding of immunology in general, the remarkable advance in experimental and diagnostic tools and the recent emergence of new indications of levamisole's interaction with immunosuppressive factors and interleukins all together warrant sufficient optimism to engage in a renewed clinical and experimental research effort. The outcome may be rewarding not only in terms of optimised treatment of patients with levamisole but also a more rational search for more potent successors may become feasible.