Cavities were prepared in 43 bicuspid teeth using two general categories of cavity depth. In the |DAdeep|DA cavities the bottom was placed in the inner third of the dentin. In the |DAintermediate depth|DA cavities the bottom was positioned in the middle third of the dentin. The bottom of the cavities was either rubbed with calcium hydroxide, covered with calcium hydroxide, or left unlined before filling according to the wet amalgam technique. The teeth were extracted after 1 week and examined histologically. All cases, except 2 with deep and 1 with intermediate depth rubbed cavities, showed local vascular dilatation in the pulp underneath the cavity. In addition, all teeth with deep unlined cavities showed inflammatory cells as did 1 with an intermediate depth unlined cavity. There were fewer displaced odontoblast nuclei in the dentin in the calcium hydroxide-treated groups. The milder reactions in the rubbed or covered groups are probably due to the restrictive effect by calcium hydroxide on penetration of amalgam components. In the teeth with deep cavities there were only minor differences between the ones which had been rubbed and those which had been covered with calcium hydroxide.