A side-effect of an intensive cytotoxic treatment on bone scanning will be reported: the socalled sickle sign, a diffuse activity arlund the calvarium seen only in patients at cytotoxic therapy. The differentiation between this harmless side-effect and abnormalities caused by the cancer could be done in our patients by a vertex view. All patients with skull metastases or meningeal carcinosis and this sign in the frontal and lateral view had an inhomogenous uptake in the vertex view. This view should therefore be added to the standard views in all patients with the sickle sign.