One major determinant of the suitability of various engineering materials for use in biological settings is the relative strength of adhesion obtained between those materials and their contacting viable phases. Maximal adhesive strength and immobility are desired for orthopedic and dental implants, for example, while minimal bioadhesion is critical to preventing unwanted thrombus formation in cardiovascular devices, plaque buildup on dental prostheses, and bacterial fouling of heat exchangers. This article reviews the principles of adhesive phenomena in such harsh environments, introduces some novel test methods and materials available for sensitive analysis of the earliest interfacial events, and provides a brief illustration of their use in the study of surface fouling of food processing equipment. Attention is then directed to adhesive phenomena in the oral environment, examining new surface conditioning methods for the prevention of micro-organism deposits, as well as the promotion of excellent tissue bonding to implanted prosthetic devices. Other bioadhesive phenomena considered include those important to the safe and effective function of new cardiovascular devices, such as the artificial heart and substitute blood vessels, and the prevention of biological fouling of materials in the sea. Comparisons of the primary interfacial events in these diverse systems--all wet, salty, and biochemically active--illustrate that Nature has been very conservative in accommodating encounters with strange boundaries. As with a classic drama, the players and timing may vary, but the script remains the same.