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 subsequent mortality. All 169,145 patients with a first HFx in Denmark during 1977-2001 were followed for up to 25 yr 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 yr, corresponding to 1,041,177 patient-years. A total of 27,834 patients had a second HFx. The cumulative incidence was 9% after 1 yr and 20% after 5 yr, 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 yr and did not normalize until 15 yr (RR = 1.01, 95% CI: 1.0-1.02). Risk factors for a 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 >85 yr), 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 higher mortality at 1 and 5 yr after a second HFx compared with the background population (men-1 yr: 27% versus 9%, p < 0.05; 5 yr: 64% versus 40%, p < 0.05; women-1 yr: 21% versus 10%, p < 0.05; 5 yr: 58% versus 41%, p < 0.05). Patients with HFx are at 2-fold risk of further HFx and the subsequent mortality is highly increased. We propose that programs for secondary prevention should be developed and tested.