[en] A method for determination and follow up of the size of inoperable intraabdominal tumours has been devised. At laparotomy, tantalum balls are deposited into the capsule of the tumour. An X-ray stereophotogrammetric method determines their position, which define a polyhedron whose volume can be computer calculated. The value of the method was proved in four patients with inoperable ovarian carcinoma, which provides a simple way for the continuous follow up of the effect of antineoplastic therapy in advanced malignant tumours. (author)