Despite the huge amount of literature available on butyltins (BuTs), few studies addressed the environmental levels of phenyltins (PhTs), octyltins (OcTs) and total tin (Sn(T)) in environmental samples. In 2006 a mussel watch survey was developed for the Portuguese coast (total of 29 sampling sites) in order to describe the concentrations of BuTs , PhTs, OcTs and Sn(T) in the whole tissues of Mytilus galloprovincialis (Lamarck, 1819). BuTs were detected in all analyzed samples accounting, in average, for 98.6% of total organotins (Sigma OTs=BuTs+PhTs+OcTs), and presented highest values in the vicinity of harbors. Tributyltin (TBT) was the dominant butyltin, representing, in average, 62% of summation operatorBuTs (Sigma BuTs=TBT+DBT+MBT) suggesting that fresh inputs of TBT are still occurring in the Portuguese coast, particularly near harbors. The contribution of organotin compounds derived from antifouling paints to the total tin levels in M. galloprovincialis is discussed.