Abstract In patients with prior hip fracture (HFx), little is known about time frame and risk factors of second HFx, as well as the ensuing mortality. The aim of the study was to elucidate the incidence of second HFx and the subsequent mortality. All 169,145 patients with a first HFx in Denmark during 1977-2001 were followed for up to 25 years and compared with the background population. Data on fractures, vital status, comorbidity, redeemed prescriptions, and socio-demographic variables were retrieved from national registers. Median follow-up was 3.8 years corresponding 1,041,177 patient years. A total of 27,834 patients suffered a second HFx. The cumulative incidence was 9% after 1 year and 20% after 5 years, being significantly higher than expected (2% and 12%, respectively, p<0.05). The RR of second HFx was 2.2 (95%CI:2.0-2.5) at 1 year, and did not normalise until 15 years (RR=1.01, 95%CI:1.0-1.02). Risk factors for second HFx were female sex (HR=1.36, 95%CI:1.32-1.40), age (HR=1.68, 95%CI:1.60-1.76 in patients above 85 years), alcoholism (HR=1.61, 95%CI:1.51-1.72), any prior fracture (HR=1.08, 95%CI:1.04-1.11), and living alone (HR=1.06, 95%CI:1.04-1.09). Both sexes had a higher mortality at one and five years after second HFx compared to the back-ground population (men one year: 27% vs. 9%, p<0.05, five years 64% vs. 40%, p<0.05, women one year 21% vs. 10%, p<0.05, five years 58% vs. 41%, p<0.05). Patients with HFx are at twofold risk of further HFx and the subsequent mortality is highly increased. We propose that programs for secondary prevention should be developed and tested.