The stability of paraffin and hydrocarbon oil dispersions stabilized by nonionic surfactants has been systematically evaluated. Using experimental design, the influence of the following parameters on dispersion stability was studied: surfactant concentration, shear rate, shear time and temperature of homogenisation. The experiments were evaluated with respect to particle size and particle migration velocity by a scanning optical analysis technique. This scanning technique monitors physical variations in a dispersion as a function of time and the technique is well suited for evaluation of dispersion stability. It was found that the only factor examined affecting particle migration velocity in a significant way was the surfactant concentration. A pronounced maximum in creaming rate was obtained at around 10 wt% surfactant both for the paraffin dispersions (suspensions at room temperature) and for the hydrocarbon oil emulsions. This surfactant-induced instability is explained as depletion flocculation caused by elongated surfactant micelles or by small oil-containing aggregates formed as microemulsion droplets during the emulsification process.