In vitro microleakage of two new combined primer/adhesive systems utilizing the all etch technique (enamel and dentin etch) with the hybrid composite resin TPH is reported. These new combined primer/adhesive systems were compared to the Optibond FL system, which consists of a separate primer and adhesive. Forty Class V preparations were cut on the facial surfaces at the cemento-enamel junction of bovine incisor teeth to a dimension of 2.0 mm x 3.0 mm x 2.0 mm with a 1.0 mm 45 degree incisal bevel. The enamel (incisal) and dentin (gingival) margins were scored separately. Results suggest that Prime & Bond provided an improvement in the gingival marginal seal over the other materials. There was no statistically significant difference in the sealing ability of the materials tested at the incisal margin.