Meniscectomy has frequently been performed on the assumption that the absence of a meniscus has little effect on joint function. Statistical analysis of data obtained from the histories, physical examinations, and roentgenographic and electrogoniometric studies of ninety-nine patients with a mean follow-up of 17.5 years after meniscectomy revealed a high incidence of poor results, degenerative arthritis, ligamentous laxity, and decreased stance-phase flexion. A meniscus should be removed only when it is definitely abnormal.