These papers were originally presented at the retirement conference for Prof. John F. Richards, which was held at Duke University on September 29–30, 2006. The conference, entitled ‘Expanding Frontiers in South Asian and World History’, brought together students, colleagues and associates of Prof. Richards to discuss themes that have marked Richards's work as a historian in an academic career of almost 40 years. These themes focused on ‘frontiers’ in multiple contexts, all relating to Richards's work: frontiers and state building; frontiers and environmental change; cultural frontiers; frontiers, trade and drugs; and frontiers and world history.