Calcium carbonate, CaCO3, is one of the most common scale components found in oilfield production wells and surface facilities. The prediction of kinetics of scale deposit depends on the understanding of the CaCO3 precipitation from solution. The formation of CaCO3 is also of practical importance in a number of areas such as in paper coatings or as fillers for rubber materials. CaCO3 precipitation studies reported in literature are based on either solution properties or using offline size/mass analysis. In the present work inline in situ technique is utilised which gives a direct measurement of the number and size of crystals. The inline image technique by FBRM, Mettler Toledo gives relatively accurate measurements. The method of moments was utilised to determine the crystal size and hence the growth rate. The effects of the solution composition on the spontaneous nucleation and the crystal growth rate have been examined. From the measurements of the crystal growth kinetic data, the crystal growth rates were estimated which are found to be an exponential function of calcium ion concentration. (C) 2007 Elsevier Ltd. All rights reserved.