Underground coal mining is associated with large quantities of gangue. In the past, the majority of gangue was not utilized but was placed in the vicinity of the coalmines forming cone-shaped dumps. Some of them contained even millions of tons of rock. Nowadays, environmental precautions extort larger utilization of any kind of waste materials, for example in road construction, civil engineering or as stowing in underground abandoned workings. Examination of the composition of waste dumps, including radioactivity, is thus an important issue. The paper presents results of a radiological survey carried out in several dumps located in the Upper Silesian Coal Basin in the south of Poland. Measurements of samples were carried out with the use of a gamma-ray spectrometer. Activity concentration results for the uranium and thorium decay chains are discussed.