A method has been described to measure the retention of luting cements to ground dentinin vitro.Using a specially designed apparatus, a circular disc of cement was produced on a ground dentin surface of equal diameter. In a universal testing machine a tensile stress was applied to the cement disc pulling it parallel with the dentin surface at right angles to the diamond grooves until separation. The effect of two different cleansing procedures on the retentive ability of two dental cements was investigated. The cleansing procedures were: rubbing ground dentin with Tubulicid®or polishing with wet pumice. The cements studied were a polycarboxylate cement (Durelon®) and a zinc phosphate cement (De Trey's Zink Zement Improved®). The retentive ability of the polycarboxylate cement showed values from six to seventeen times those of the zinc phosphate cement. The retentive ability of zinc phosphate cement was only slightly affected by the two cleansing procedures, while for polycarboxylate cement it was somewhat reduced following rubbing with Tubulicid and greatly improved after polishing with pumice and water.