In the first edition, published in 1976, Professor BOMBELLI demonstrated a clear alternative to total hip replacement that is also useful in cases of advanced osteoarthritis. Since then the number of osteotomies perfor med has reached 2500, which together with the longer follow-up of the original cases means that the author has significantly more experience with his new techniques. He has refined his previous concepts of the pathogenesis and treatment of osteoarthritis, and with the benefit of his experience has further clari fied the indications and contra-indications of valgus-extension and varus osteotomy. Valgus-extension osteotomy has been proven to be particu larly effective in cases with well-formed osteophytes and elliptical femoral heads. On the other hand, the indication for varus osteotomy has mostly been restricted to cases in which the femoral head is spherical. The role of CHIARI and SALTER pelvic osteotomies in those cases in which the coverage of the femoral head is insufficient is not neglected. Osteotomy is capable of complementing and accelerating the healing process, particularly in young patients in whom hip function is still well preserved and in whom there is early radiological evidence of sponta neous, osteophyte-dependent repair. Whenever feasible, pre-existing or anticipated leg length inequalities are adjusted intra-operatively, but when this is technically impossible a postoperative lift may be required.