The Relict Gull (Larus relictus) is considered vulnerable due to its declining world population. Non-breeding season ecology of this species is poorly understood. Recent observations on wintering Relict Gulls indicated that Bohai Bay, Tianjin municipality, China, is important for this species. From 2003-2005, surveys were carried out there in order to provide data on distributions, numbers and population structure of the gulls during the non-breeding season. The results show that Bohai Bay is of international importance for Relict Gulls based on the 1% Ramsar criterion. The maximum wintering flock was composed of 3,362 individuals, which is nearly one third of the world population. Proportions of the three age groups (first-year, second-year and adult) changed through the migration season. Loss of intertidal flats and human disturbance are regarded as the main threats to the gulls. Further surveys on population size, distribution and age structure should be conducted along the coasts of southern Bohai Bay and the Yellow Sea during the winter in the near future.