A series of 325 diagnostic and operative arthroscopic procedures were reviewed--the growing importance of this technique was underlined. An open meniscectomy was performed in 235 cases after diagnostic arthroscopy. In 45 cases meniscal flap was removed arthroscopically. In 7 cases chondral or osteochondral loose bodies were removed, in 5 cases the hypertrophic synovial fold was cut, in 3 cases staples or fixation screws were removed and 3 diagnostic biopsies were carried out. No significant complication was observed. It was stated that arthroscopy makes diagnostics more precise, enables performing some operations without opening that joint, reduces of treatment and its costs.