Since the original descriptions of the involvement of crystals in arthritis, understanding of the clinical syndromes of gout and pseudogout and the role of basic calcium crystals in arthritis has increased. Gout is a common problem in middle-aged males but has an increasing prevalence in older patients, particularly women. Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease is now a well-recognized problem in older patients. The diagnosis of both of these common forms of arthritis and the need to individualize therapy in patients with other medical problems remain important clinical challenges to the practicing physician.