The dataset comprises a diverse set of physical, chemical and biological data including: bacteria, carbon, chlorophyll, dissolved gases, light levels, nutrients, phytoplankton, productivity, respiration, salinity, temperature, trace elements and zooplankton. Measurements were gathered from the North Atlantic and Norwegian fjord waters between 1971 and 1998. The data arise from three sources: biological and hydrographic data collected between 1971 and 1975 at Ocean Weather Ship (OWS) India in the North Atlantic; conductivity-temperature-depth (CTD) casts, water samples, net samples and meteorological data from the four week Bergen Mesocosm experiment at Espegrend Marine Biological Field Station (Norway) in 1995; and the six week RRS Discovery cruise 221 to the North East Atlantic in 1996, where physical, chemical and biological data were collected. The data were collected using a variety of methods including: more than 500 CTD and SeaSoar profiles; nearly 1000 water bottle samples; over 600 net hauls; over 450 Secchi disk deployments; nearly 4000 multisizer samples; 23 production experiments; four drifting buoy tracks and 40 days of weather observations. The PRIME programme aimed to lay the basis for mathematical models to describe the role of plankton in biogeochemical fluxes within the oceans which have implications for climate regulation. The project was hosted by the School of Ocean Sciences, University of Wales, Bangor. Data management was undertaken by the British Oceanographic Data Centre and over 95% of the data collected are now assembled on a CD-ROM. The data are accompanied by an extensive users' guide (covering sampling protocol documentation), the structures used to store the data, and the data interrogation tools.