The Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) is endemic to the middle and lower reaches of the Yangtze River, China. It is the only freshwater population of porpoises in the world and is currently listed as Endangered by IUCN. In November and December 2006, we used two boats and line transect methods to survey the entire current range of the population, except for two lakes (Poyang and Dongting). When on-effort, one boat surveyed 3,100 km with 240 sightings and a mean group size of 1.87 resulting in 0.077 sightings/km, while the other boat surveyed 3,065 km with 198 sightings and a mean group size of 2.05 resulting in 0.065 sightings/km.