The Mediterranean-Alpine Experiment (MEDALPEX) data set comprises over 200,000 hourly sea level measurements. Data are included from 28 sites around the northern coast of the Mediterranean and one in the Atlantic at Cadiz. Measurements were collected from December 1981 and September 1982, with a special observing period (SOP) between 15 February and 30 April 1982. Twenty eight coastal sites were instrumented with conventional stilling wells, while one offshore site off Corsica used a bottom pressure recorder. The data are stored, together with benchmark information, as time series at each site with hourly values of sea surface elevation recorded to the nearest millimetre. The aim of the MEDALPEX Experiment was to study the role of atmospheric forcing on the dynamics of the Western Mediterranean. Data were supplied by laboratories in Belgium, France, Monaco, Italy, Spain, UK and former Yugoslavia. Responsibility for assembling, quality controlling and analyzing the sea level data collected during MEDALPEX was vested in the British Oceanographic Data Centre (BODC).