A compilation of the chemical data and brief review of the mineral zirconolite, essentially CaZrTi207, is presented. A total of 321 chemical analyses, 169 previously unpublished, from 39 of the 46 known terrestrial localities, and covering IO rock types are tabulated. A brief description of the minerals associated with zirconolite is outlined for each locality. Data from all zirconolite-bearing lunar rocks have also been compiled. The recently published nomenclature scheme for zirconolite is employed throughout.