To determine the outcome of subtrochanteric fractures treated by intramedullary (IM) nailing and identify causes for implant failure. We performed a retrospective analysis of all subtrochanteric fractures treated by intramedullary nailing in Belfast trauma units between February 2006 and 2009. This subgroup of patients was identified using the Fractures Outcome Research Database (FORD). Demographic data, implant type, operative details, duration of surgery and level of operator were collected and presented. Post-operative X-rays were assessed for accuracy of reduction. One hundred and twenty two (122) patients were identified as having a subtrochanteric fracture treated by IM nailing. There were 79 females and 43 males. Age range was 16 to 93 (mean 78). 95 (78%) cases were performed by training grades and 27 (22%) by consultants. Duration of surgery ranged from 73–129mins (mean 87mins). 47 patients (38.5%) were found to have a suboptimal reduction and 75 patients (61.5%) had an anatomical reduction on immediate post-operative x-ray. One year from surgery 73/122 patients were available for follow up. Of those patients with suboptimal reduction, 13/47 (27.7%) required further surgery. 8 required complete revision with bone grafting, and 5 underwent dynamisation. A further 6 patients had incomplete union. In the anatomical group, 4 patients underwent further surgery (5%). 3 required dynamisation and one had exchange nailing for an infected non-union. 3 patients had incomplete union at last follow up. 5/47 (10.6%) had open reduction in the suboptimal group compared to 25/75 (33.3%) in the anatomical group. Of the 27 cases performed by consultants, 13 (48%) were open reduction, compared to 17/93 (18%) by training grades. This study has shown that inadequate reduction of subtrochanteric fractures, leads to increased rates of non union and ultimately implant failure. We recommend a low threshold for performing open reduction to ensure anatomical reduction is achieved in all cases.