The principal objective of the CLIWOC project was to realise the scientific potential of logbook climatic data and to produce a database of daily weather observations for the world's oceans between 1750 and 1850. Another objective was to provide a comprehensive understanding of the nature of climatic change over the oceans for the century after 1750 when logbooks became abundant and to link with existing databases such as the I-COADS dataset (International Comprehensive Ocean-Atmosphere Data Set). The study period is also significant because it marks a period when climatic change cannot be seen as a consequence of world-wide industrialization and the release of greenhouse gases into the atmosphere. The files of the Dutch part of the CLIWOC dataset are divided into three major clusters: 721 Access database files, 418 digitized ships' logbooks (jpg-files) and 369 webpages. These clusters are described under 'Data collections'. One of the project's main achievements was the preparation of a database drawing on British, Dutch, French and Spanish naval logbook records for the immediate pre-instrumental period (1750-1853). This database is freely available on the KNMI website (http://www.knmi.nl/cliwoc/cliwocdata.htm).