The tumbling melt granulation (TMG) method by a centrifugal fluidizing granulator (CF) without any use of organic solvents was applied as a coating technique for preparing controlled-release spherical beads. The core beads containing four kinds of drugs with different solubilities : nicotinamide (NA), isoniazid (ISA), theophiline (THEO) and salicylic acid (SA), were driven in the CF and were previously heated at 61-63°C before feeding powdered hydrogenated castor oil (HCO) to the CF. HCO was gradually fed and adhered on the surface of the core beads. At the bed temperature of 61-63°C, about 20% of the HCO was presumed to have melted. After the adherence of HCO, the coated beads were cooled at room temperature and thus the controlled-release beads were obtained. The dissolution rates of these coated beads were determined by use of the JP paddle method. The rates seemed to increase with an increase in the solubility of the drug. To clarify the mechanism of drug transport through the coated layer of HCO, the superposition method was applied for the dissolution profile of the coated beads with various coating levels. Then, in each of ISA, THEO, and SA, the dissolution curves were superposed completely, irrespective of their coating level. Permeability coefficients, P values of each drug calculated for various pH media, were coincident, irrespective of pH. These facts indicated that the limiting factor of the dissolution of HCO coated beads was diffusion, and that the permeability of the coated layer was pH independent. The equilibrium P values decreased with the increase in solubility of the drug. The partition coefficient between the layer surface and inner core medium, activity coefficient, viscosity, diffusion through waxy phase and so on, might be attributed to these phenomena.