The Second International Manx Shearwater Workshop took place between the 2nd and 4th August 2005. It was hosted by Copeland Bird Observatory (CBO), was held at the Ulster Museum in Belfast, Northern Ireland, and was attended by 90 delegates from around the world. The First International Manx Shearwater Workshop took place in Madeira in 2000 and attendees included an enthusiastic group from CBO who volunteered to host a second workshop. In planning the event, we aimed to attract a wide range of interests by extending the focus from Manx Shearwater Puffinus puffinus and related petrel species to include petrels breeding in the North Atlantic. We invited papers on four broad themes: populations and censusing; conservation issues (threats to breeding colonies and protection measures); activity at the colony (breeding behaviour and population ecology); and activity away from the colony (at-sea behaviour and censusing).