The goal of adjuvant chemotherapy is to treat postoperative microscopic disease in the hope of preventing tumor recurrence and/or metastasis. Since the introduction of chemotherapeutic agents, the disease-free survival of children with medulloblastoma has improved only modestly. Therefore, there is a need to develop and investigate new chemotherapeutic agents for this malignancy. Gallium nitrate has demonstrated significant antineoplastic activity toward human medulloblastoma in vitro and in vivo and may prove to be an optimal chemotherapeutic agent in treating medulloblastoma microscopic disease. The present study consisted of injecting medulloblastoma Daoy intradermally into both flanks of nude mice. A 15-day 50-mg/kg/day regimen was implemented the day after tumor inoculation. All treated and control mice received saline hyperhydration during the treatment period. The interval between tumor cell inoculation and first measurable tumor detection, tumor occurrence, growth rate, and size were recorded. Results indicated that gallium nitrate significantly prolonged the interval between tumor cell inoculation and measurable tumor detection.