Displaced femoral neck fractures are known to be associated with high rates of mortality. The purpose of the present study is to investigate pre- and postoperative factors which influence this mortality in a series of 1186 consecutive Danish patients presenting to one hospital's orthopaedic department with Garden type 3-4 fractures. Subsequent mortality data was obtained from the state population register (224 were still alive). The stepwise Cox proportional hazards model was used for multivariate analysis in order to obtain the predictors of postoperative mortality. The median survival of male subjects fell from 5.2 years in an age-matched control population to 1.6 years in the patients. In women survival time fell from 6.6 to 2.8 years. Almost all excess mortality occurred during the first 3 months following hemiarthroplasty. In order of significance, key factors negatively influencing mortality at 3 months were: cardiac complications, dementia, male sex, age, waiting time before operation, stroke and dislocation of the prosthesis and perioperative fracture. Of these, waiting time for surgery and dislocation of the prosthesis could be modified. A number of other studies have confirmed the importance of optimising these factors.