Censuses offer snapshots of a given population at a particular point in time. In presenting a static picture of a dynamic process, such snapshots might reveal much about the composition and spatial distribution of the population in question, but they shed no light on its past development and are therefore unable to illuminate its likely future course. Without history, censuses lack a predictive quality. Recognizing this fact, the designers of the Census of Marine Life have incorporated an historical dimension into their scheme of study. This strand of the wider project, dubbed the ‘History of Marine Animal Populations’ (HMAP), will generate new, validated historical databases that will be fed into the Ocean Biogeographic Information System (OBIS). To test the feasibility of this process, it is intended that a pilot study (H-OBIS) will be conducted in 2001.