Dispersions of hydrophobic substance e.s. resin emulsions, usually having a relatively low average particle size can be continuously and speedily prepared by feed a hydrophobic substance in the liquid state into at least two static mixers, arranged in a series. The resin is introduced at a temperature above 50 degrees C. but below its degradation temperature of hydrophobic substance and water under pressure is introduced into the first mixer. The mixture of resin and water is passed to another mixer maintained at a temperature lower than that prevailing in the first mixer and below the boiling point of water. Optionally aqueous solution of surfactant under pressure instead of water is introduced into the first mixer and optionally aqueous surfactant is introduced into the second mixer.