The aqueous pigmented inkjet ink formulator is faced with a large number of potential commercially available grades of organic pigment. This paper presents data that explores the link between the properties of some commercially available organic pigments and (i) the particle size achievable in dispersed form and (ii) the subsequent effects on the stability of the dispersion to particle migration. Different grades of the same organic pigments from several manufacturers were dispersed under equivalent conditions and particle sized using Photon Correlation spectroscopy. Ink jet inks were formulated from these dispersions and the propensity to settling was measured using a Turbiscan stability analyser. The results show a clear correlation between rate of sedimentation and particle size. The effects of particle size are less pronounced as ink viscosity increases. Correlation with the available physical parameters of the pigment powder is not always clear, however the study shows the importance of selection of the appropriate grade of pigment in optimising the achievable particle size. Examples are shown that illustrate the colouristic advantages of reduced particle size.