This liber amicorum, offered to Dirk van de Kaa on the occasion of his retirement as Professor of Demography at the University of Amsterdam, opens with a biography and a bibliography. The core of the book is formed by 32 essays in honour of Van de Kaa, written by colleagues and friends from all over the world, who have in common that in one way or another their paths have crossed his. Most of them are demographers, and the topics they chose for their contribution cover almost the entire range of demography and often connect to the activities and scientific topics for which Dirk van de Kaa has become so well-known, such as the Second Demographic Transition. Next to these demographic contributions, the book contains several essays from other disciplines, such as physical planning, geography, sociology, history, and general literature. Dirk van de Kaa retired as Professor of Demography at the University of Amsterdam at the end of 1998. He has played an important role in both Dutch and international demography since the early 1970s. He was the first Director of the Netherlands Interuniversity Demographic Institute, Scientific Secretary of the Royal Commission on Population, represented the Netherlands in the Population Commission of the United Nations, played a crucial role at the UN Population Conferences in Bucharest (1974), Mexico City (1984) and Cairo (1994), and was active in the International Union for the Scientific Study of Population (IUSSP) and the European Association for Population Studies (EAPS), which he founded. Van de Kaa also played an important role in establishing the postgraduate programme in demography pdoD (currently nethur-Demography).