Abstract: Slow release drug delviery granules comprising porous granules of a calcium phosphate compound having an atomic ratio of Ca to P of 1.3 to 1.8, a porosity of 0.1 to 70%, a specific surface area of 0.1 to 50 m.sup.2 /g and a pore size of 1 nm to 10 .mu.m, fired at a temperature of 200.degree. to 1400.degree. C., and a drug component impregnated in pores of the granules, and a process for producing the same. The drug delivery granules of the present invention have a controllable, prolonged effect of drug release and a good imaging property to an X-ray or ultrasonic wave, and therefore can be advantageously utilized in the field of chemotherapy.