[en] Purpose: To describe early outcome and technical treatment aspects of four patients with pediatric genitourinary malignancy receiving local therapy using interstitial brachytherapy at the Peter MacCallum Cancer Institute since 1991. Methods and Materials: Two patients with primary bladder tumors and two patients with primary vaginal tumors received interstitial brachytherapy with needle-template techniques following chemotherapy. Two patients were treated for salvage following local failure after primary chemotherapy and two patients electively after initial induction chemotherapy, one following limited surgical excision. Three patients were treated exclusively with brachytherapy with doses of 50-55 Gy (LDR), and one patient also received external beam radiation. Results: Resultant implants, dosimetry, and dose prescriptions are described and illustrated. Follow-up is short (14-27 months), but all patients remain well without significant sequelae. One child required salvage surgery for local failure. Conclusion: Interstitial brachytherapy using needle-template techniques described is an ideal method of local ablative therapy for pediatric genitourinary malignancy. Functional and late sequelae should be less than that of radical surgery or external beam radiation. There are technical and practical advantages compared with other brachytherapy techniques described in the literature