To estimate the effect of delay to surgery for hip fracture on 30-day mortality using a risk adjustment strategy to control for the effect of demographic and clinical confounders. This observational study was carried out on all patients admitted with a hip fracture and discharged between January 2004 and December 2007 from a teaching hospital. Gender, age, time to surgery, mortality and medical comorbidities were derived from hospital discharge records (SDO), while International Normalised Ratio (INR) and American Society of Anaesthesiologists (ASA) score were retrieved from clinical records. Backward stepwise logistic regression was used to identify potential confounders in the relationship between time to surgery and mortality. A final multivariate logistic regression analysis was carried out controlling for the effect of confounders. In the 1320 patients who underwent surgery (mean age = 83 years, % female = 76.8%), time to surgery was two days or less in 746 (56.5%) patients and 30-day mortality was 3.5%. The interventions included partial or total hip replacement (N=820, 62.1%) and reduction and internal fixation (N=500, 37.9%). Multivariate logistic regression analysis showed that patients with a time to surgery greater than two days had a 2-fold increase in 30-day mortality after adjusting for age, gender, and comorbidity (OR=1.992, 95% CI 1.065-3.725). In a second model also including ASA score the odd ratio decreased to 1.839 (95% CI 0.971-3.486). Patients with a hip fracture should have surgery within two days from admission in order to reduce 30-day mortality.