Summary.The histological response of periapical tissues to root canal fillings with Sealapex, pure calcium hydroxide and gutta‐percha points was studied in dogs' teeth. After putpal extirpation the root canals were enlarged, irrigated and dried. Teeth in the first group were filled with gutta‐percha points alone, those in the second group were filled with pure calcium hydroxide and gutta‐percha, and those in the third group were filled with Sealapex and gutta‐percha. The animals were killed after 7, 30 and 90 days and histological sections of each specimen were prepared. It was concluded that hard tissue formation was more pronounced after root filling with Sealapex than with calcium hydroxide or gutta‐perc