Conical intersections play important roles in photochemistry and photobiology through their preeminent control over the course of electronic relaxation processes. In this Letter, we present results from a combined experimental and computational study of ultrafast internal conversion in nucleic acid bases and intramolecular charge transfer in N,N-dialkylaminobenzonitriles, which indicate that these photoprocesses occur through three-state conical intersections involving an intermediate electronic state. (C) 2008 Elsevier B.V. All rights reserved.