Objectives: To evaluate the tissue reaction of some pulpar protecting materials. Method and Materials: Standardized implants of calcium hydroxide (CH), glass-ionomer cement (GIC), and light-cured dentin adhesive (LDA), surgically introduced into the dorsal connective tissue of Wistar rats, were left for 15 and 30 days. For each of the 2 experimental times, a respective sham group (S) was studied. After experimentation, animals were sacrificed, and the material from implant sites was removed and studied with light microscopy and stereology (volume density of interstitial fibrosis, Vv[f], and numerical density of mast cells per area, NA[mast cell]). The implants and the surfaces of the fibrous capsule were analyzed with scanning electronic microscopy (SEM) adapted with microanalysis. Results: The CH group had the smallest value of Vv[f] and the LDA group the greatest. At day 30, the Vv[f] of the LDA group showed an increase of 30% and was different from that of the CH group in the same period (P .05). The NA[mast cell] was smaller in both the CH and the S group than in the LDA group (P .05). The GIC group had intermediate values for Vv[f] and NA[mast cell] between CH and LDA values. There was light fibrosis in the surgical area with few mast cells associated to vessels in the S group. SEM detected presence of silica fragments in the fibrous capsule of the LDA group and calcium in the fibrous capsule of the CH group. Conclusions: All tested materials allowed healing of the implanted area; tissue reaction was smallest in the CH group. Keywords: biocompatibility, calcium hydroxide, dentin adhesive, fibrosis, glass-ionomer cement, mast cell, stereology