Stockholm archipelago is the largest connected archipelago in Swedish waters, and extends 200 km along the east coast. It is about 100 km wide off the city of Stockholm. The topography includes valleys, cliffs and rifts. The many biotopes, including open waters, rocky coasts, narrow fjord-like bays and sheltered inlets, house a rich flora and fauna. We describe the pelagic and benthic communities and the environmental status of Stockholm archipelago. The inner archipelago has suffered from severe eutrophication for most of the 20th Century. Nutrient levels are still high but declining, and environmental conditions have gradually improved in the pelagic zone during the last 10-20 years. The sediments have been heavily contaminated by metals and organic pollutants since the early 1900s, especially in the inner archipelago. Concentrations of these pollutants peaked around 1960-1980, but have declined since then.