Salcombe Harbour and the Kingsbridge Estuary are situated on the south coast of Devon and are constituted by a steep-sided main channel with branches. The length of the main channel is 8 km from the entrance to Kingsbridge in the north. The area covered by water at high tide is about 4 km^2. There are extensive areas of intertidal sediments in the estuary which are sandy in Salcombe Harbour but of mud further north and in the creeks. Some sediments have coarse shale and shells mixed in. Rocky shores extending into the subtidal occur at the entrance and at promontories within the inlet. There is very little freshwater inflow and conditions are almost fully marine along most of the main channel. The area is mainly used for recreational sailing and there are extensive moorings and pontoons. There is little fishing activity and few oyster cultivation trays. The area is used by field courses and collecting occurs especially at two particularly rich sites. The scientific importance of the shores from a marine biological point-of-view is well established and the whole inlet including the seabed is to be notified as an SSSI. The area was first surveyed and sampled thoroughly in 1900 and since then, staff at the Marine Biological Association at Plymouth have made collections and observations in the area particularly of burrowing species and their commensials and the decline of Zostera marina at Mill Bay. The present survey aimed to collect further information on the marine habitats and communities, particularly those in the subtidal, which had not been sampled since 1900, and from intertidal and subtidal rocky areas which had never been thoroughly surveyed. Also, survey and sample sites were planned to cover the areas sampled by Allen and Todd in 1900 so that comparisons could be made. The abundance of species living on hard surfaces and visible on the surface of the sediments was recorded in situ. Burrowing fauna were collected in cores by digging in intertidal areas and samples were sieved over 0.5mm, 1mm and 5mm mesh sieves. Subtidal sediments were sampled using a pipe dredge and, at the entrance, a suction sampler. The samples were sieved over a 1mm mesh. Animals were picked out of the sediments, identified and individuals of each species counted. Photographs were taken to illustrate habitats, communities and species and a series of aerial photographs was taken during extreme low water level in April. Habitats and communities present were classified into nine intertidal and twelve subtidal types. Descriptions are given of each of these and the abundance of species is shown in tables. The distribution of habitats and communities is discussed and the changes on moving from the open coast to the most sheltered parts of the estuary are listed. The main characteristics of marine communities in Salcombe Harbour and the Kingsbridge estuary are the same as in 1900 except that a few well-recorded species have disappeared or been reduced in abundance. These losses have in part, been linked to the loss of Zostera marina due to disease in the 1930's and to accumulation of sand in some areas. Recently, the abundance of dog-whelks, Nucella lapillus appears to have declined dramatically and the antifouling coating Tributyltin is suspected as the cause. Incoming species include Mya arenaria, a native species which invaded the south coast about twenty years ago, and Laminaria ochroleuca, a southern species which was first observed in Britain in 1948 and at Salcombe in 1949. Alien species are also present and, most recently, Sargassum muticum has colonised the estuary and is now abundant. Our surveys added substantially to the amphipods and polychaetes known from sediments, doubtless because of the smaller mesh size we used to screen samples compared to previous studies, and to the flora and fauna recorded from hard substrata which had not previously been surveyed in any detail. The scientific interest and nature conservation importance of the area has been assessed using standard criteria and the conservation importance of the habitat and communities in the area have been provisionally graded as of Local, Regional, National or International importance. The assessment of importance of sediment-dwelling species requires further consideration. Salcombe Harbour and the Kingsbridge Estuary are of outstanding scientific interest mainly for the burrowing fauna present in both intertidal and subtidal sediments and because of the presence of many rare or unusual species in both intertidal and subtidal areas. Current levels of recreational usage do not appear to pose a significant threat to the scientific interest of the area but digging for specimens and bait at extreme low water level, the effects of Tributylin anti-fouling paints and the possible impact of Sargassum muticum on the rich sediment-dwelling fauna are all cause for concern. Records currently considered sensitive have been removed from this dataset.