An adhesive tape comprising a backing and a layer of adhesive on the backing. The backing comprises a biaxially oriented substrate which comprises an isotactic polypropylene composition. The tapes and backings of this invention can be severed readily using commercial tape dispensers having metal or plastic cutting teeth to produce cleanly serrated cut edges on the tape. The biaxially oriented substrate is preferably made from a resin comprising an isotactic polypropylene homopolymer having a melt flow rate greater than 8 grams/10 minutes, more preferably greater than 12 grams/10 minutes, and still more preferably greater than about 20 grams/10 minutes. One preferred way to obtain such a resin is to blend: A) at least one isotactic polypropylene homopolymer "A" having a weight average molecular weight of at least 350,000 grams/mole and melt a flow rate of about 0.5 8 grams/10 minutes, more preferably about 0.5 5 grams/10 minutes; with B) at least one isotactic polypropylene homopolymer "B" having a weight average molecular weight of at least 100,000 grams/mole and a melt flow rate greater than 8 grams/10 minutes, and preferably greater than about 20 grams/10 minutes, and more preferably greater than about 50 grams/10 minutes.