Hypofractionated treatment of low risk prostate cancer by external beam are planned and delivered using rotational arc (RA) treatment planning on a conventional linac. Treatment plans are generated retrospectively on helical Tomotherapy (HT) for comparison. Eight low risk prostate patients were implanted each with three commercial beacons. RA plans were generated on an Eclipse planning system and delivered using CBCT image guidance for localization and real time tracking of beacons. Dose fractionation was 7.25 Gy/fx for 5 fractions to a total dose of 36.25 Gy. Planning goals were set for 95% of the planning target volume (PTV) to receive at least the prescription dose. Treatment plans were also generated on a HT planning system using the same fractionation and dose-volume constraints. Margins for the PTV were set at 5 mm in all directions except 3 mm posteriorly. Treatment plans were evaluated based on the target coverage measured by minimum, mean and maximum dose to the target volumes in the dose-volume-histogram (DVH) analysis and the conformity index (CI).The heterogeneity of the dose distribution in the PTV was measured by a dose heterogeneity index as DHI. The volumes covering 5, 10, 20, 50 and 70% of the prescription dose (V5, V10, V20, V50 and V70) for two OARs were determined. The mean age of the patients was 61 y (range 53-79) and the mean prostate volume was 49.1 cm3 (range 30.3-77.4 cm3). The mean PSA value was 7.0 ng/mL (range 3.8-8.91). All patients were staged at T1cN0M0 except for one at T1bN0M0. For the RA plans the average values of monitor units (MU), actual beam delivery time, CI and DHI are 3193, 328.6 s, 1.194 and 2.88, respectively. The equivalent biological dose at 2 Gy/fx (EQD2) for the SBRT treatment was 90.63 Gy with an a/b ratio of 1.5 for prostate. For HT plans, the average values of the monitor units, treatment beam-on time, CI and DHI are 14330, 984.9 s, 1.307 and 3.22, respectively. Analysis of the DVH data shows that, on average, the minimum dose coverage of the PTV for RA plans is 4% higher than the HT plans. The averages of the maximum and mean dose coverage of the PTV for the two planning systems are almost same. The average monitor unit and beam-on time for HT plans are 4.5 and 3 times, respectively, higher than the RA plans. Thus the RA treatment is more efficient. The CI of the RA plans is slightly better than the HT plans – the average being about 10% lower for the RA plans. Also, the dose heterogeneity of the PTV in the RA plans is around 12% lower than the HT plans. Comparison of the averages of the minimum, maximum and mean doses for the rectum and bladder shows no statistical difference between the two planning systems.