Abstract: A pharmaceutical oral controlled release multiple-units formulation is prepared by mixing units containing an active substance and coated with a substantially water-insoluble, but water diffusable controlled release coating with particles of an active substance, the mean size of which is at least one power of 10 smaller than the coated units under conditions which will result in adherence of the smaller particles to the surface of the controlled release coating in a substantially uniform layer. The coated units have a mean size of between about 0.1 and 1.5 mm, in particular about 0.4 to 1.2 mm, and the fine particles have a mean particle size of from about 1 to about 50 .mu.m and are present in the composition in an amount of at the most 25 percent by weight, in particular at the most 5 percent by weight and preferably not more than 1 percent by weight, calculated on the weight of the coated units.