[en] An improved pharmaceutical radioactive capsule consisting of a non-toxic, water soluble material adapted to being ingested and rapidly disintegrating on contact with fluids of the gastro-intestinal tract is described. Each capsule is provided with filler material supporting a pharmaceutically useful radioactive compound absorbable from the gastro-intestinal tract. The capsule is preferably of gelatin, methyl cellulose or polyvinyl alcohol and the filler is a polyethylene glycol. The radioactive compound may be iodine e.g. sodium radioiodide I-131 or 123. The capsule may also contain a reducing agent e.g. sodium thiosulphate, sulphite, or bisulphite. (author)