Polyurethane-based pressure-sensitive adhesive which attaches strongly to polar plastic surfaces, smooth metal surfaces and glass, but which has weak, if any, adhesion to paper, paperboard or skin and is easily detachable without damaging surfaces during its removal, and is reusable. The adhesive comprises a polyurethane formed by reacting an aliphatic or alicyclic polyisocyanate having a functionality of equal to or less than three with a combination of diol and triol.