Leakage studies are used for evaluation of the sealing quality of fillings. This method is very popular due to its technical simplicity and inexpesivity. However, the final extent of dye penetration is influenced by a number of factors. The technique of root canal instrumentation and obturation, as well as the type of materials used, are the factors of major importance. Nevertheless – the type of colour indicator (its size, concentration, pH, chemical reactivity), time from obturation to immersion, immersion period itself, the technique of sample preparation and evaluation – can also negatively influence final results. This procedural heterogenity can be the main cause of disagreement amongst different authors. The aim of this review was to present the most frequent factors that can negatively influence the results of leakage studies.

        Key words: leakage studies – tightness of a seal – review