Our aim was to evaluate the impact of deep wound infection after hip fracture surgery on functional outcome and mortality. Two thousand, two hundred and seventy-six consecutive surgically treated patients with non-pathological fractures, aged over 50 years (mean age 78.3 years), were followed up prospectively. The 29 patients who had deep infection (rate 1.3%) and who received revision surgery were compared with controls without infection, matched for age, sex, residential status at fracture, fracture type, treatment method and walking ability. When the functionality of hip fracture patients was evaluated four months after the primary operation, the patients with deep wound infection had impaired walking ability (P=0.039) and required walking aids, including wheelchairs, more often than the control patients (48% vs 20.8%, P=0.022). At four months, the mean duration of hospitalization at the primary hospital was significantly longer for the cases than the controls (P<0.001). Diabetes was more common in the patients with deep infection (P=0.038). Staphylococcus aureus was the most commonly isolated micro-organism, and it was associated with higher one-year mortality (57%) than the other bacteria (14.3%, P=0.014); the overall mortality of the infected patients and controls was 34.5% and 24.1% at one year, respectively (P=0.508). In conclusion, deep infection after a hip fracture operation impairs short-term functional outcome and slightly increases mortality, with an excess mortality rate of 10.4%.