The effect on the pulp of a high-copper amalgam was studied in buccal cavities in 16 pairs of human premolars, 32 teeth, restored with ANA 2000. To minimize the risk of bacterial contamination, the cavities were treated with a cleanser, Tubulicid, and the outer portion of the filling was replaced by zinc oxide-eugenol cement (ZOE), i.e. surface-sealing. In one cavity in each pair, the control, a thin lining was used. The teeth were extracted after 5-13 days, sectioned, stained with hematoxylin-eosin or Brown and Brenn and evaluated for the degree of pulpal inflammation and presence of bacteria. The results showed that regardless of whether lining was used or not, no inflammation or only a very few inflammatory cells were found in the 21 teeth in which the thickness of the remaining dentin varied from 0.15 mm to 0.5 mm, except for one pair showing slight to moderate inflammation. However, in this pair bacterial growth were found on the cavity walls. No other teeth showed bacterial growth. In the remaining eleven teeth the thickness of the remaining dentin was less than 0.08 mm, including five pulpal exposures. Slight to severe inflammation occurred in eight of these teeth. ANA 2000 per se did not seem to irritate the pulp except in very deep cavities or on direct exposures. The reason for this reaction is not known, but it might be attributable to the zinc content of the amalgam.