A new Czech regulatory leaching test according to the decree No. 338/1997 Code was used to assess the leachability of selected inorganic contaminants, in particular heavy metals, from fly ash. The fly ash was collected from an electrostatic precipitator in a power station fuelled with North-Bohemian brown coal. An influence of the main parameters of the test, such as the weight of the sample, solid-liquid ratio, duration of the leaching and the way of agitation was investigated. A satisfactory repeatibility of the leaching test was found for most elements (RSD 10%) except for As (RSD ca. 33%), Fe (RSD ca. 20%), Cu (RSD ca. 13%), and Ba (RSD ca. 10%). As the new Czech regulation is compatible with some foreign standards (DIN 38414/4, draft of the European standard prEN 12457), the results obtained in this paper could be generalized.