The purpose of this in vitro study was to evaluate microleakage of tooth colored restoratives and accompanying single step adhesive systems using two drying methods (syringe air versus "sponge" applicator blotting). Eighty teeth were randomly assigned to four material groups. Class V cavity preparations, located half in enamel and half in cementum at the cementoenamel junction (CEJ), with a 1.0 mm enamel bevel were completed. The adhesive/composite groups included: (1) Single-Bond/Z-100 Composite, (2) Prime & Bond 2.1/Dyract AP Compomer, (3) OptiBond Solo Plus/Prodigy Composite, and (4) Scotchbond MultiPurpose/Z-100 Composite. Each material group (n=20), consisted of preparation Subgroups dried with syringe air (A), (n=10) and sponge applicators (B), (n=10). The preparations were conditioned, rinsed, and gently dried followed by placement of the primer/adhesive and restorative materials. All teeth were thermocycled, stained with methylene blue dye, invested in clear acrylic resin, and sectioned longitudinally through the center of the restoration. Readings were taken at the occlusal and gingival surface positions of each restoration section. A ratio (%) of wall length to amount of leakage along each wall was established. One-way Analysis of Variance (ANOVA) testing revealed: (1) no significant (p<0.05) differences existed between materials at the occlusal surface position in Subgroups A and B (syringe vs. applicator drying), (2) significantly (P<0.05) greater leakage of OptiBond Solo Plus compared to Single-Bond, Prime & Bond 2.1, and Scotchbond MultiPurpose at the gingival surface position in Subgroups A and B, (3) significantly (p<0.05) greater leakage of OptiBond Solo Plus compared to Single-Bond and Scotchbond MultiPurpose, combining the occlusal/gingival surface position scores, (4) no significant difference existed between Single-Bond Subgroups A/B, OptiBond Solo Plus Subgroups A/B, Scotchbond MultiPurpose Subgroups A/B, (5) significantly (p<0.05) greater leakage of Prime & Bond 2.1 Subgroup B compared to Subgroup A, (6) no significant (p<0.05) difference existed between material groups, except OptiBond Solo Plus (occlusal vs. gingival surface position), (7) no significant (p<0.05) difference between Single-Bond, OptiBond Solo Plus, and Scotchbond MultiPurpose comparing both Subgroups, same materials, and surface positions, and (8) no significant (p<0.05) difference existed between Prime & Bond 2.1, comparing both Subgroups, occlusal surface position. In the present study, significantly greater leakage was revealed with OptiBond Solo Plus compared to the other material groups, especially at the gingival surface positions. Significantly greater leakage was also recorded with OptiBond Solo Plus and Prime & Bond 2.1 sponge applicator drying as compared to the same materials, syringe air drying.