This cross-disciplinary project resulted in a diverse data catalogue. This includes meteorology (2-D wind speed and direction, total irradiance, Photosynthetically Active Radiation/PAR, air temperature, atmospheric pressure, humidity); atmospheric composition (chemical analyses of aerosol particle composition) and biological, chemical and physical properties and processes in the photic zone (optical properties of the water column; chlorophyll concentration; photosynthetic pigment composition; primary production; bacterial production; phytoplankton and bacterial speciation; concentrations of biogenic trace compounds such as iodocarbons, methyl bromide, dimethyl sulphide/DMS and dimethyl sulphoniopropionate/DMSP; trace gas production; plankton community composition; nutrient concentration; concentrations of trace metals such as iron; salinity; temperature; Dissolved Organic Matter - particulate carbon, nitrogen and phosphorus; phytoplankton growth rates, grazing mortality and viral lysis; ammonium regeneration, nitrification and nitrogen fixation; gross production, net community production and dark community respiration; zooplankton ecology). The fieldwork included two dedicated research cruises in the eastern North Atlantic Ocean, spanning the period April - May 2004. Measurements of nutrient cycling and biological activity were monitored prior to and after deployment (IN stations) of patches fertilised with iron and phosphate relative to several (OUT stations) controls. Measurements were taken using a variety of instrumentation, including conductivity-temperature-depth (CTD) profilers with attached auxiliary sensors and acoustic Doppler current profilers (ADCPs), while incubation chambers were used for shipboard experiments. Samples were collected with Niskin bottles attached to the CTD frame at different depths in the water column and samples analysed onboard or preserved for analysis back in the laboratory. The FeeP data set was intended to advance understanding of how the supply and mutual interactions between iron and phosphate control biological activity and fluxes in the subtropical North Atlantic. The study led by the Plymouth Marine Laboratory (PML) united marine scientists from institutions across the UK and international collaborators. It was funded by the UK Natural Environment Research Council. The data are held at the British Oceanographic Data Centre (BODC) and have been incorporated into the National Oceanographic Database (NODB).