The incidence of complications from arthroscopic surgery is low. Between 1978 and 1991, 8500 arthroscopies were performed by the two senior authors (J.N. and D.R.A.D.). Several significant complications were recorded, and these are presented to show how they occurred, and how our practice of arthroscopy was subsequently modified. There were four cases of clinically detectable deep vein thrombosis of which three were associated with pulmonary embolus, three cases of haemarthrosis, two deep infections, three compartment syndromes with one case of impending compartment syndrome, six cases of instrument failure and one case of persistent synovial fistula.