Precipitation processes are widely used in industry for the production of particulate solids. Efficient mixing of the reagents influences the development of supersaturation in the reaction environment and therefore the particle characteristics. Intensified modules can provide a new route for obtaining improved mixing and this paper illustrates an experimental investigation using narrow channel reactors for the precipitation of calcium carbonate by reacting aqueous solutions of calcium nitrate and sodium carbonate. Two channels of square cross sectional area, having a diagonal line of 1 x 10(-3) and 2 x 10(-3) m, respectively, were used and experiments were carried out by varying flow rates and reagent concentration. A flow visualization technique has been used to understand the flow behaviour in the reactor channels, which were also characterized by calculating the specific power input transmitted to the reagents. The calcium carbonate slurry was analysed for particle size and dispersity with a Malvern Mastersizer 2000. Images of the particles were obtained by using an optical microscope connected to a digital camera and a scanning electron microscope (SEM). Selected samples were also analysed by X-ray diffraction. Limited batch experiments were conducted for benchmarking the performance of the narrow channel reactors.