During a ten year period (1978-1988) 565 patients, aged 70 years and over, suffering a fresh pertrochanteric fracture have been treated in the Department of Traumatology at the University Hospitals of Leuven, Belgium. According to the system of Evans and Jensen, 388 fractures were classified as unstable. Special attention was given to the 324 cases of type I C and I D fractures. The method of treating greatly changed during the period of study. All patients were followed up prospectively during one year. Our study showed that for these unstable fractures, fixation with an angled plate or Ender nails should be forsaken. The overall results of the dynamic hip screw treatment were good (reoperation rate 2%, good functional results in 64%), but as this treatment has a risk for serious collapse and pain in about 80% of all type I D fractures, one could suggest to treat these complex multifragment fractures primarily with an endoprosthesis. This treatment needs no longer to be considered as a severe intervention, as the danger of mechanical complications being very minimal (less than 1%).