The aim of this laboratory study was to obtain basic information on the leachability of the priority pollutants in the Theisenschlannm. Beside the German standard leaching test applying distilled water, a serial concentration buildup test (a five-step shaking cascade) for the simulation of drainage water from sludge ponds was used. In addition, a special aspect of Theisenschla1mm weathering, the influence of acid rain deposition, was investigated by using the pH_stat shaking test. The leachate analyses have been focused on heavy metals, arsenic and on polycyclic aromatic hydrocarbons (PAH), but we have also perform1ed a screening on other leachable organic substance classes with gas chromatography/mass spectrometry (GC-MS). None of the Theisenschlamm leachates provide any cause for radiological concern. Chemical analyses of leachates show that relevant regulatory criteria for surface dumping are exceeded for Zn, Pb, Ni and Cd and for selected PAHs. The much greater mobilization of these elements and of arsenic at pH_stat = 4 than under neutral conditions has to be considered in a worst case scenario because the tests showed also that Theisenschlamm has an acid neutralization capacity of only 900 mmol H⁺/kg.