Objective: Recent studies have demonstrated that acid etching of vital dentin and pulpal tissue does not retard pulpal healing, odontoblastoid cell differentiation, or dentinal bridge formation when the pulp is capped with adhesive resins. The purpose of this study was to evaluate the pulpal response in nonexposed and exposed monkey pulps to treatment with the Clearfil Liner Bond 2 and Clearfil AP-X system. Method and materials: Class V and Class I cavities in nonexposed and exposed pulps were observed at 7 or 8, 27, and 97 days. Results: There were no differences in pulpal inflammation between the Clearfil Liner Bond 2/Clearfil AP-X specimens and calcium hydroxide controls in either Class V or Class I cavities at the various time periods. Conclusion: Clearfil Liner Bond 2 and Clearfil AP-X system is not toxic to either nonexposed or exposed pulpal tissues when placed according to manufacturer's directions.