Poly(biphenyl dianhydride-p-phenylenediamine) (BPDA-PDA) polyimide film surfaces are initially modified with KOH aqueous solution to yield a potassium polyamate surface. The reaction of the polyamate surface with acid gives a polyamic acid surface. The starting polyimide surface is reproduced upon curing the modified surface. Modified surfaces are identified with X-ray photoelectron spectroscopy, external reflectance infrared (ER IR) spectroscopy, and contact angle measurement. The average depth of modification, which is measured by a method using an absorbance-thickness relationship established with ellipsometry and ER IR, is controlled by the reaction temperature and time. Surface topography and film thickness can be maintained while a strong polyimide-polyimide adhesion is achieved. A relationship between surface structure and adhesion is established. © Copyright 1991 American Chemical Society. © 1991, American Chemical Society. All rights reserved.