For many patients with STS, administering adjuvant radiation treatments in the form of interstitial brachytherapy provides an excellent alternative to a protracted course of EBRT. Ideal patients are those with intermediate- or high-grade tumors amenable to en bloc resection. Attractive features of this approach include an untainted pathologic specimen, expeditious completion of treatment, reduction in wound complications, and improved functional outcome. Brachytherapy can permit definitive reirradiation by tightly localizing the high dose radiation exposure. It is also useful in patients who are known to have or be at high risk of metastatic disease, for whom the rapid completion of local treatment allows systemic therapy to begin quickly. Introduction of HDR techniques has shifted the delivery of brachytherapy from inpatient solitary confinement to an outpatient setting. Early reports using HDR brachytherapy for treatment of adult and pediatric STS are quite encouraging. The clinical equivalence between hyperfractionated HDR schedules and traditional LDR techniques is gaining acceptance.