Aphidicolin is a fungal derived tetracyclic diterpene antibiotic. It is selectively toxic for neuroblastoma (NB) cells in vitro but has no significant effects on the viability of normal human cells and a variety of other tumor entities. We evaluated the antitumoral effects of the water soluble ester aphidicolin glycinate (AphiG) on established human NB xenografts from UKF-NB-3 cells in athymic (nude) mice. Furthermore, we explored the efficacy of direct intraneoplastic and systemic delivery of AphiG. Systemic administration of AphiG (60 mg/kg intraperitoneally, twice per day on 10 consecutive days) significantly suppressed tumor growth but was not able to induce any cures. In contrast, intratumoral AphiG injections (60 or 40 mg/kg/twice a day for 4 days) induced complete tumor regression. Two weeks after the end of treatment no tumor cells were microscopically detectable. Animals were free of tumor for more than 90 days. Histologic examination of inner organs and bone marrow did not reveal any apparent toxic effects of AphiG. These data strongly indicate that AphiG deserves further evaluation as a specific treatment for neuroblastoma.