The authors have performed 65 Chiari osteotomies in adults. The results have been studied with a follow-up ranging from one to 12 years. Details of the surgical technique are described. Fifty-three cases have had satisfactory results. Forty-five cases have a follow-up of more than 5 years and among these, 38 still have a very satisfactory result. It is concluded that Chiari osteotomy may stop the development of early arthrosis clinically as well as radiologically in more than two-thirds of dysplasias or subluxations in patients younger than 50 years. When there is associated femoral dysplasia it should be corrected either simultaneously or preceding the osteotomy.