AbstractIn-situ precipitation of calcium carbonate in bagasse fibers resulted in a very significant increase in specific scattering coefficient and consequently large improvements in opacity and brightness of the handsheets made from such pulp. At the same level of filler loading, the scattering coefficient of in-situ precipitated pulp was much greater than for directly loaded pulp. In-situ precipitation of calcium carbonate caused a drop in strength properties of bagasse pulp, but such loss could be recovered to a large extent by blending with other pulps. The effect of in-situ precipitation of calcium carbonate on pulp fibers was quite different for bagasse pulp from hardwood pulp. In-situ precipitation of calcium carbonate on hardwood fibers showed neither much improvement in optical properties nor much reduction in strength properties.