INTRODUCTION: To identify variables associated with primary anatomical outcome following vitrectomy and internal tamponade for rhegmatogenous retinal detachment (RD). METHODS: A retrospective analysis of prospectively collected data, using a database of RD treated with vitrectomy and internal tamponade. Collected data complied with the RCOphth Retinal Detachment Dataset. The main outcome measure was anatomical failure within six months of surgery. RESULTS: There were 6377 vitrectomies. 869 eyes were excluded, either because no outcome was recorded, or inadequate follow up, leaving 5508 operations for analysis. 63.9% of patients were male, and the median age was 62. Primary anatomical failure occurred in 13.9%. On multivariate analysis, the following were associated with increased risk of failure: age <45, or >79, inferior retinal breaks, total detachment, one quadrant or greater inferior detachment, low density silicone oil, and presence of proliferative vitreoretinopathy. C2F6 tamponade, cryotherapy, and 25 G vitrectomy, were associated with reduced risk of failure. The area under the receiver operator curve was 71.7%. According to this model, 54.3% of RD are at low risk (<10%), 35.6% are at moderate risk (10-25%), and 10.1% are at high risk (>25%) of failure. CONCLUSIONS: Previous attempts to identify high risk RD have been limited by small numbers, the inclusion of both scleral buckling and vitrectomy, or by excluding some types of RD. This study examined outcomes in unselected RD, treated by vitrectomy. Identification of the variables associated with anatomical outcome after RD surgery enables accurate risk stratification, which is valuable for patient counselling and selection, and for future clinical trials.