Background: Although no prospective studies have compared functional results of trochanteric osteotomy and a non-trochanteric approach, most surgeons feel that trochanteric osteotomy is outdated in simple hip arthroplasty. Reasons not to perform an osteotomy include the fear of longer rehabilitation and worse (final) functional outcome. METHOD: This prospective study examines differences in rehabilitation between posterolateral and trochanteric approach one year post-surgery using questionnaires (WOMAC, SF-36, HHS) and functional tests (walking, climbing stairs, rising from sitting, and strength tests). Of the 109 patients 24 had a trochanteric osteotomy: the selected approach was based on the surgeon's preference. The trochanteric osteotomy group included more patients with developmental dysplasia of the hip. Before the start of the study no power analysis was performed. Results: Data from the questionnaires showed no significant differences between the two groups at 3, 6 and 12-months follow-up. At 3-months follow-up patients in the trochanteric osteotomy group scored lower on the functional tests. This difference had disappeared at 6 and 12-months follow-up, except for abduction force which remained lower in the trochanteric osteotomy group in patients with a non union of the TO. Conclusion: For simple hip arthroplasty an approach without osteotomy seems a logical choice. Although the power of this study is low, in experienced hands trochanteric osteotomy seems to give good functional results at 6-12 months post surgery if trochanteric union is obtained. Therefore, one should not hesitate to perform an osteotomy in difficult cases.