Loch Sween is one of 7 locations identified in Great Britain as proposed statutory marine reserves. In order to provide information to assist in management of these areas, basic survey work to describe littoral and sublittoral habitats and communities is being carried out. This report presents results from a littoral survey of Upper Loch Sween, and an assessment of scientific interest and nature conservation importance of the sites surveyed. Sites were selected to include areas likely to be of high conservation importance and a range of shore types. Most sites were located in Linnhe Mhuirich or around the rapids area at the entrance to Linnhe Mhuirich, with several additional sites in Caol Scotnish and on the west shores of Loch Sween. Two small brackish-water lakes were also examined. A brief description of the habitats and main biotic subzones present at each survey site is given. Plants and communities present in the survey area are classified into types according to habitat and height on the shore, and described in more detail using posted data from similar sites. An assessment of scientific interest and nature conservation importance of the shores at the sites surveyed was limited to the littoral subzone and sublittoral fringe, and it was considered that sublittoral populations are likely to be of more interest. The international, national, regional or local importance of sites was not assessed since this requires more detailed knowledge of other locations, particularly on the west coast of Scotland. Criteria used were applied in the sense of the NCC 'Handbook for the Preparation of Management Plans'. The main points in the assessment were: 1) The sites surveyed showed a generally low diversity of shore types, species and habitats, which was largely attributable to the very sheltered nature of all sites surveyed. Diversity of species increased greatly at and below low water. 2) The shores are good, with extensive examples of sheltered sea-loch communities and growth forms present, and as such may be useful for specialised research and education. However, the sublittoral fringe at many sites, particularly the Linnhe Mhuirich Rapids area, has many large or delicate growth forms which could be easily damaged by trampling. 3) Several species of plants and animals of scientific interest were recorded. Records currently considered sensitive have been removed from this dataset.