Soon after it was first marketed in 1976, colorless cubic zirconia became the dominant diamond imitation, with current production of approximately 60 million carats per year. Although cubic zirconia was discovered as a natural mineral in 1937, crystals usable for faceting were first produced in 1969 and it was not until a practical skull-melting technique was developed in the USSR in 1972 that commercial production became feasible. This article reviews the skull-melting technique used to produce cubic zirconia and examines the current status of this diamond simulant with regard to quality, production, and market. The patent situation is discussed, as well as prospects for new diamond imitations and the recent surge of interest in colored cubic zirconia. Also included is an Appendix summarizing the technical and gemological data for cubic zirconia and its distinguishing characteristics.