Intra-articular crystals (monosodium urate monohydrate, calcium pyrophosphate dihydrate, basic calcium phosphates) can cause acute and chronic inflammation and joint damage. Identification of the crystals by polarized microscopy is the key step in diagnosis but improved reliability of synovial examination is required. Treatment of disorders associated with gout or calcium pyrophosphate deposition may reduce non-joint morbidity and assist treatment of the arthritis. Various forms of anti-inflammatory therapy work for acute crystal-induced arthritis; prompt commencement is usually more important than which option is used. In gout, recurrent attacks are usual, but hypouricaemic therapy is almost never urgent, is life-long, and is too often negated by poor compliance. In most patients, allopurinol or any of the potent uricosuric drugs will allow maintenance of normouricaemia but renal failure, renal calculi, transplantation, and allopurinol allergy narrow the options and complicate management.