The Joint North Sea Data Acquisition Project (JONSDAP) dataset comprises hydrographic and meteorological time series, including current velocities, water temperature (both at the sea surface and at depth), hydrographic pressure, air temperature, barometric pressure and wind velocities. The data were collected in the North Sea from March-June 1976. Automatically recording current meters (and usually temperature sensors), off-shore tide gauges, thermistor chains and meteorological data buoys were deployed at numerous locations around the study area for periods of a few days to several weeks. Data from 9 tide gauge, 4 meteorological data buoy, 10 thermistor chain and 81 current meter deployments are held at the British Oceanographic Data Centre (BODC). Additional hydrographic data were collected during JONSDAP 76 cruises, while over-flights with aircraft provided further measurements. However, these data are not stored at BODC. JONSDAP 76 consisted of two parts: FLEX, the Fladen Ground Experiment between 25 March and 15 June, and INOUT, the inflows of water of the whole North Sea as well as the internal movements from 15 March to 25 April. The data were collected by 13 laboratories in 8 countries.