Chronic hepatitis B is a viral infection that can currently only be treated with interferon-α and nucleosidic inhibitors of viral polymerase — 3TC and adefovir — but these treatments are limited by serious side effects and a high failure rate. Novel therapeutic regimes are urgently required. In the February 7 Science, Karl Deres and colleagues at the Bayer Research Center, Wuppertal, Germany, describe a substance class for the treatment of HBV infection that displays a highly specific antiviral inhibition of capsid formation, concomitant with a reduced half-life of the core protein (Science 299:893-896, February 7, 2003).