Previous studies with four rapid in vitro and in vivo test systems have shown that the epoxy resin-based root canal sealer AH26 may be genotoxic and cytotoxic (9). The purpose of this study was to determine the cytotoxic and genotoxic effects of the new resinous root canal sealer AH Plus by means of the growth inhibition test with primary human periodontal ligament fibroblasts and permanent 3T3 monolayers, the procaryotic umu test, the eucaryotic DNA synthesis inhibition test, and the in vivo alkaline filter elution test. In addition, Ames tests were performed with extracts from AH Plus. AH Plus caused only slight or no cellular injuries. Furthermore, no genotoxicity and mutagenicity were revealed by AH Plus. These data should be taken into consideration when deciding about a root canal sealer.