The B-mode images of 32 patients affected with a malignant melanoma of the choroid were studied, in particular with respect to choroidal excavation. The degree of visibility of choroidal excavation at the B-scan was compared with the thickness of the choroid, scleral invasion, vascularisation, retinal detachment and the reflectivity of the tumour. None of these histological and echographical features appeared to be significantly related to the degree of the visibility of choroidal excavation. Also the condition of the choroid was studied. At examination of all the histological sections no choroid was found between tumour and sclera. This implies that choroidal excavation should be visible at echograms in every case instead of only in 75\% of the cases as was found for our series.