The deposition in situ of calcium carbonate inside glass capillaries was studied as a function of the temperature, the flow rate of the solutions, the concentration ratio of calcium and carbonate ions, the capillary radii, and the solution volumes which flowed through the capillary. Calcium carbonate was precipitated just before the inlet to the capillary from sodium carbonate and calcium chloride solutions. Two series of experiments were conducted in two separate laboratories, and despite the difference in relative depositions, some common features of the deposition process were found. Thus, maximum deposition occurred around 65-degrees-C. There were optimum flow rates, 0.60-0.80 ml/s, of the solutions for maximum deposition to occur. The deposition was very sensitive to the concentration ratio of calcium and carbonate ions. For example, the deposition at a ratio 5:1 (calcium to carbonate ion concentration) was more than twice that for an equimolar 1:1 ratio of the ions. The results indicate that the deposition of calcium carbonate is determined by the balance of attractive and repulsive forces. The forces are of Lifshitz-van der Waals, acid-base (hydrogen bonding), and electrostatic nature. It seems that the electrostatic forces between the glass surface and calcium carbonate particle, as well as between calcium carbonate particles, play an important role in the deposition process. The maximum deposition occurring around 65-degrees-C coincides with a change of the precipitate crystallographic structure, from calcite into aragonite, at this temperature.