The Hedonistic Imperative outlines how genetic engineering and nanotechnology will abolish suffering in all sentient life. This project is ambitious but technically feasible. It is also instrumentally rational and ethically mandatory. The metabolic pathways of pain and malaise evolved only because they once served the fitness of our genes. They will be replaced by a different sort of neural architecture. States of sublime well-being are destined to become the genetically pre-programmed norm of mental health. The world's last aversive experience will be a precisely dateable event.