This paper deals with the stability of dilute dispersions of copper phthalocyanine in organic solvents, a subject of importance to the paint and ink industries. It has been found that quite small surface potentials (a few millivolts) are sufficient to stabilize the dilute dispersions of the particles in solvents of low dielectric constant (possibly because this would be a constant charge system) though insufficient to stabilize particles in solvents with dielectric constants above about 20. Addition of organic acids enhanced the particles' stability, probably by a proton-exchange mechanism, and addition of an organic-soluble electrolyte, tetrabutylammonium bromide, caused all systems to flocculate. The presence of a polymer at concentrations above about 1% caused flocculation to occur, probably by a depletion mechanism. The attractive depletion energy increased with polymer concentration, resulting in the sedimentation volume increasing with polymer concentration.