This volume covers Leg 81 of the cruises of the Drilling Vessel Glomar Challenger. During the first International Phase of Ocean Drilling (IPOD) of the Deep Sea Drilling Project (DSDP), several passive margins were drilled in the Atlantic Ocean and the Gulf of California by means of a series of transects designed to address the evolution of passive margins in part as a function of relative age. During Leg 81, a systematic transect of five holes across the entire west margin of Rockall Plateau was designed by the Passive Margin Panel with the specific objectives of documenting the nature of the dipping reflectors and the evolution of the margin in time and space. Leg 81 of the IPOD Phase II of the Deep Sea Drilling Project began in Southampton on 27 July 1981 and ended 56 days later in Ponta Delgada, San Miguel, Azores. During the leg, Glomar Challenger drilled eight holes at four sites.