The purpose of this study was to test the viability of human pulp fibroblasts on certain dental materials after their direct application. the materials tested were: Dycal®, Calxyl®, a calcium hydroxide-suspension (0.001137g Calxyl®/ml medium), zinc oxide-eugenol, the glassionomer cement Ketac-Molar® Aplicap® and the dentin adhesive OptiBond SoloTM. At first we used all materials in a 96well assay and then we repeat the study in a 24well assay with the calcium hydroxide-containing materials only. To measure the viability, the viability test EZ4U was carried out in the two assays after 3, 6, 12, 24, 48 hours and 4, 8, 16 and 32 days. The result of both assays suggest, that the direct application of aqueous calcium hydroxide-suspensions will show the lowest decrease in viability of human pulp fibroblasts. Keywords: pulp, fibroblasts, cells, cultured, biocompatibility, dental materials