This paper reports on bonding characteristics of assemblies using as substrates poly(vinyl chloride) (PVC), acrylonitrile-butadiene-styrene (ABS) and polypropylene (PP), and as melt adhesives an ethylene-vinyl acetate (EVA) copolymer, a polyurethane (PUr), and low density polyethylene (LDPE). Peel strength measurements on freshly assembled joints were compared with results for samples aged under inert and humid conditions. Significant time-dependent variations of bond strength were observed in all cases, but the direction of change varied among the assemblies. Those involving only dispersion-force materials displayed losses of bond strength, attributable to the gradual accumulation of cohesively weak layers at the substrate/adhesive interface. In assemblies involving materials able to interact by non-dispersion (acid/base) forces, as indicated by inverse gas chromatographic data, a variety of responses was obtained. These have been rationalized by the ability of the EVA and PUr adhesives to reorient when in contact with an appropriate polymer substrate. Reorientation, leading to bond strength increments, was associated with substrate/adhesive pairs (e.g., PVC/EVA and ABS/PUr), in which significant acid/base interaction could take place.