The coasts of Britain harbour a diverse seaweed flora comprising more than 600 species. This abundant natural resource has been widely used by humans, and has played an important part in the development of the socio-economy of Scotland, especially in the western coastal regions. Although the use of seaweeds was of greater social and economic importance in the past, domestic and industrial seaweed use continues in Scotland today. Domestically, seaweed has been used as a source of medicine, food, fodder and fertiliser, and appears in popular Scottish folklore. Industrially, seaweed was formerly used as a source of soda and potash for the glass and bleaching industries, and also as a source of iodine. These industries have typically followed a ‘boom-bust’ pattern. More recently seaweeds have been harvested for the alginates, fertiliser, cosmetics and health food industries. In addition, they have been used as biomonitors of pollution. Although there are a growing number of industries using seaweed in Scotland, strong international competition has threatened the livelihoods of local small-scale collectors, and most of these industries are now supplied by foreign sources.