Purpose: CT-based 3-dimensional volumetric dose planning, when used with multichannel brachytherapy applicators, has demonstrated utility in certain settings such as in the post-lumpectomy treatment of breast cancer. A parallel situation exists for patients in need of transvaginal brachytherapy (e.g. post-hysterectomy for endometrial cancer). The purpose of this study is to evaluate the feasibility of this approach, using a new flexible, expandable applicator for vaginal cuff brachytherapy. Materials and Methods: Patients were identified as candidates for transvaginal brachytherapy in accordance with current FIGO guidelines. In 14 cases, a flexible, multi-lumen expandable vaginal applicator (CAPRI applicator) was inserted into the introitus in a low profile configuration, advanced to the vaginal vault and then expanded in-situ with saline until the device was held firmly in the vaginal canal. A pelvic brachytherapy external compression garment was used to help secure the applicator in position. No Foley or rectal catheters were used. The pelvic area was imaged via CT and a 3-dimensional dose plan was created, using an evenly spaced array of up to 13 available source lumens within the applicator. Bladder and rectum were fully contoured. The target volume was nominally a 5mm expansion of the applicator surface, with localized reductions (2e4mm expansions) at regions immediately adjacent to the bladder and rectum. Coverage was 90/100. After simulation, the patient returned on subsequent alternate days for applicator placement and dose delivery. Applicator position was monitored closely, with regard to any potential intra-fraction changes in applicator depth, rotation, fill volume and diameter. Dose was delivered via a remote high-dose-rate afterloader in accordance with relevant dose and fractionation schemes (e.g. 700cGy to depth x 3). Results: CTebased 3-dimensional dose planning with the flexible, expandable multi-lumen applicator provided for an anatomically conformal dose delivery. Monitoring of applicator position confirmed intra-fraction consistency, thereby allowing the same dose plan to be administered to that patient on subsequent fractions. Simulation and dose delivery were well tolerated by the patients and were easily adopted by the nursing, dosimetry and physics staff. Avoidance of the rigid applicator clamp and other indwelling catheters expedited applicator placement and contributed to patient comfort. Conclusions: CTebased 3-dimensional dose planning, when used with a new flexible, expandable multi-lumen vaginal applicator is feasible and allows for highly conformal dose delivery to the targeted tissue. Well received by patients and brachytherapy technical staff, this approach may play an increasing role in the treatment of endometrial cancers and other cancers that benefit from vaginal brachytherapy.