Beam's-eye view (BEV) based three-dimensional conformal therapy (3DCRT) treatment planning is being utilized with increasing frequency in the treatment of prostate cancer. This trend has been driven, in part, by the desire to escalate radiation doses, which may require superior targeting precision. However, conformal therapy for prostate cancer has also been advocated a t lower doses partly due to retrospective studies that demonstrate improvements in quality of life by reducing acute toxicities. Such benefits of 3DCRT need to be confirmed in prospective studies as well as justifications for the additional costs in patients receiving conventional doses of radiation. A randomized study of patients undergoing radiotherapy (RT) to BEV-based treatment volumes S. hand reconstruction of treatment volumes from computer tomography (CT) images was conducted to assess acute toxicities. Patients with clinical stage B and C disease were randomized to undergo either BEV treatment planning (Group I) (n = 17) or CT-based hand reconstruction of treatment volumes (Group II) (n = 18). Both groups underwent standard prostate irradiation with 4 fields and conventional doses (65-70 Gy). Patients were evaluated weekly during treatment for acute rectal and bladder toxicity (RTOGLEORTC grades 0-IV). Acute bladder and rectal toxicities increased over the course of therapy in both groups of patients. No statistically significant differences in weekly mean acute bladder toxicity (based on RTOGLEORTC grades 0 to IV) was seen with patients in Group I (week 1: 0.06; week 2: 0.29; week 3: 0.62; week 4: 0.35; week 5: 0.65; week 6: 0.60) vs. Group 11 (week 1: 0.22; week 2: 0.32; week 3: 0.72; week 4: 0.67; week 5: 0.86; week 6: 1.08). The mean weekly acute rectal toxicity for BEV-based planning (week I: 0.00; week 2: 0.41; week 3: 0.75; week 4: 0.94; week 5: 0.75; week 6: 1.07) was also not statistically different from hand reconstruction (week 1: 0.11; week 2: 0.42; week 3: 0.47; week 4: 0.53; week 5: 0.62; week 6: 0.62). Comparison of the two arms of the study failed to demonstrate an advantage to BEV therapy when the distribution of toxicities were analyzed by chi-square or Wdcoxon rank-sum test. No difference in severity of bladder toxicity was noted by RTOGLEORTC grade (P = 0.78); one patient in each group experienced grade 3 toxicity. No patients experienced grade 3 or 4 rectal toxicity; however, BEV therapy was associated