Kinetics of irreversible deposition of positively charged melamine latex particles on mica sheets bearing a negative charge was investigated experimentally in a sedimentation cell using the direct microscope observation technique. By extrapolating the kinetic runs to long times the maximum density of the monolayers formed under various ionic strength was determined. It was found that particle deposition rate obeyed the ballistic deposition mechanism, rather than the previously studied random sequential adsorption (RSA) mechanism, due to the relatively high specific density and size of the particles. However, as for the RSA model, the decrease in the monolayer density for low ionic strength could be interpreted quantitatively in terms of the effective hard particle concept.