Introduction: Preoperative short course radiotherapy (SCRT) is considered a standard treatment in the management of locally advanced rectal cancer. However, in southern European countries, preoperative chemoradiotherapy is the preferred option, leaving SCRT only for those patients not suitable for combined treatment. Our aim was to retrospectively analyze the outcome of patients who have been treated with SCRT in our Institution. Methods: From 2006 to 2017, 68 patients (p) (50 men and 18 women) with a proven biopsy of adenocarcinoma of the rectum were treated with SCRT in our Department. The median age at diagnosis was 74 years (42-86). All patients were evaluated in a multidisciplinary tumor board and the reasons to indicate SCRT were: age> 80 years (25p), presence of synchronous metastases at diagnosis (21p), heart disease (7p), synchronous intestinal tumors (12p), unknown reason (3p). Dose delivered was 25 Gy in 5 fractions of 5 Gy, administered in prone position by 3D-conformal radiotherapy (3DCRT), with photons of 6-18 MV. In 65 (95.5%) patients, surgery was performed in the week following the end of 3DCRT. Results: With a mean follow up of 40 months, no acute or chronic toxicity was observed. Median overall survival (OS) was 42 months, median specific cancer survival (SCS) was 59 months and median disease-free survival (DFS) was 56 months. The 5 years OS, SCS and DFS was 43.5%, 59.6%, and 48.7% respectively. Only 2 local recurrences were observed, one of them in a patient who refused surgery once 3DCRT was finished. In the univariate data analysis, no significant difference was observed in the SCS or OS nor in the analysis of the SCRT indication subgroups, neither in the location of the tumor (lower 31%, middle 47%, upper 20% or unknown 2%). According to the staging we did not observe any differences in survival. However, for patients with T4 tumors median survival was 16 months, versus no T4 patients, in whom median was not reached (p < 0.001). In patients with a positive margin in the surgical specimen, the median survival was 43 months compared with negative margin patient subgroup in which median survival was not reached, with trend to significance (p 0.056). Adjusted to the state of the surgical margin, only T4 tumor was an independent factor in multivariate analysis for worse survival, with an estimated risk of death 5 folds higher than the rest of the stages (p 0.022). Conclusion: Despite being a group of selected patients with poor vital prognosis (due to age, metastasis or heart disease), we obtain a median overall survival of 59 months and only 2 local recurrences, with an excellent profile of acute and chronic toxicity, for all subgroups of patients and all tumor locations. In our analysis only T4 was a predictor for worse results.