In expert opinions about poisonings by inorganic compounds, difficulties may arise that are associated with unavailability of data on concentrations of metals and non-metals in various biological materials, occurring normally and in poisoning cases, lack of appropriate material for analysis and lack of screening methods of analysis. Furthermore, the nature of the inorganic compound itself, its mode of action and metabolism in the organism may cause problems. This paper mainly focuses on the issue of appropriate selection of materials for analysis, on the basis of selected poisoning cases.