The PIROP (Programme Intégré de recherches sur les oiseaux pélagiques) data set, Atlantic subset, consists of geo-referenced vessel-based surveys to monitor pelagic seabirds. Most surveys were carried out by R.G. B. Brown from 'vessels of opportunity' supplied by the Bedford Institute for Oceanography (BIO) in Dartmouth/Halifax, but many other platforms and observers were used, too. During these surveys observations other than seabirds were also recorded, e.g. Waterfowl, Waterbirds, Songbirds, Raptors, Owls, Sea Mammals, and other sightings of interest (weather, oceanography, vessel activities, bird behaviour, etc.). The data collection period covers all seasons of 1966-1992, with most surveys being conducted between (late) summers of 1975-1987. The survey protocol originally consisted of unlimited width 10min transects, but was changed appr. 1984 towards a Tasker et al. (1984) type of survey (fixed-width strip transect). However, data and results from the PIROP database need to be interpreted as relative, and not absolute, abundance.