Aspects of the production and dissolution of CaCO 3 hard parts dominate the literature regarding contemporary marine chemistry and paleoceanography. During my long career I have contributed more than 200 papers related to this subject. In this prefatory article in the first volume of the Annual Review of Marine Science, I recount what I consider to be the highlights of my attempts to understand the cycle of CaCO 3 in today's ocean and in oceans of the past. These studies began in the Bahamas in the early 1960s and then quickly graduated to the world ocean. Although much of my research has involved stable and radioisotopes contained in shells and coral directed toward reconstruction of the late Quaternary operation of the earth system, in this review I concentrate on carbonate chemistry and, in particular, the compensation in the deep sea for the overproduction of CaCO 3 by marine organisms.1