The purpose of this in vitro study was to determine the relationship between the shear bond strength [SBS] of seven dentin bonding systems to dentin and the quantitative microleakage [ML] of Class V preparations in dentin restored with these systems. The systems evaluated were All-Bond/Bisfil-P [A]; Syntac/Heliomolar [B]; XR-Bond/Herculite [C]; Scotchbond 2/Silux [D]; Denthesive/Charisma [E]; Prisma Universal Bond 2/Prisma AP.H [F]; and Tenure/Perfection [G]. The 115 specimens were removed from the assembly apparatus and stored in saline at 37 degrees C for 24 hours, the SBS determined and expressed in MPa. Fifteen Class V preparations in dentin were restored with each of the bonding systems, thermocycled 500x in 2% methylene blue solution between 50 degrees C and 8 degrees C, and the ML determined by means of a spectrophotometric dye-recovery method. The ML was expressed in microgram dye/restoration. The data were analyzed by ANOVA, Student-Newman-Keuls test, and linear regression analysis. The SBS in MPa were: A:17.2 +/- 3.6; B:15.9 +/- 2.1; C:15.4 +/- 3.7; D:11.6 +/- 2.2; E:10.7 +/- 3.7; F:10.4 +/- 2.5; G:8.2 +/- 3.9. The ML in microgram dye/restoration were: A:2.6 +/- 1.2; B:2.6 +/- 1.0; C:2.2 +/- 1.9; D:3.1 +/- 2.9; E:4.6 +/- 4.2; F:2.6 +/- 2.5; G:4.4 +/- 4.1. SBS = 20.91-2.60 [microgram dye]. The results suggest that a SBS of +/- 21 MPa may reduce ML to near zero.