TThis study aimed at assessing whether proanthocyanidin, a collagen cross-linker, affects the adhesion strength of resin composites on the dentine surface. Freshly extracted, caries-free, human molars (N=55) were embedded in transparent resin and bisected. The halves were then assigned to either a treated or a non-treated group, where the treatment consisted of a 10 min incubation in a 6.5% proanthocyanidin solution in PBS. A resin composite cylinder was polymerized perpendicularly to the dentinal surfaces and shear tests were made, using an Instron-like machine. The fracture surfaces were characterized by optical (Picro-Sirius Red stain) and electron microscopy (FESEM EDX analysis). Mean bond strength values were 10.73 MPa (SD 3.70) for the treated group and 8.69 MPa (SD 3.20) for the non-treated group (p less than 0.05 Students t-test). No constant fracture patterns could be found within the two groups. Proanthocyanidin treatment may improve the adhesion properties of the dentine-bonding interface.