Jura and Islay are the most southerly and two of the largest islands of the Inner Hebrides. Their ecology and demography is sharply controlled by geology, and the marine enviroment is also affected by the unusual hydrography. Jura, 50 km long and 10 km wide, is composed mainly of quartzite, which forms the west coast with numerous caves and spectacular raised boulder beaches above present high water mark. Loch Tarbert opens to the sea half way along this coast, almost cutting the island in half. In the east, phyllites and schists form ridges parallel to the shore which enclose north and south facing bays. The times of high water differ by as much as five hours from one side of the island to the other, giving rise to strong tidal currents through the Sound of Islay, the Sound of Jura and the Gulf of Corryvreckan. Islay is 45 km long and 35 km wide, with a complex geology and varied typography. It is dissected by two large sandy lochs, Gruinart and Indaal, and the coastline includes stretches of dunes, cliffs, gullies and rock platforms. Tidal currents are not as strong as Jura, except in the shared Sound of Islay, but, similarly to Jura, the shore hydrography is unusual. The report is based on two surveys, carried out in October 1979 and June 1982, and differences in results obtained by the two teams are discussed. Some are thought to be due to differences in methods and access to shores at low tide, whilst others are clearly natural variations. A total of 58 stations, covering 40 sites were visited. Some are very close together and similar, thus not all are discribed individually in the report, although all descriptive data has been entered on data sheets lodged with the Nature Conservancy Council. Many phyla are recorded, but some seriously under-recorded, and many specimens collected have not yet been fully identified and are available in the Royal Scottish Museum for future research. The report states that, on the whole, the shores of Jura and Islay were found to be rather disappointing, the low species richness reflecting the lack of variety of microhabitats in the more sheltered areas, although some species of mollusca were found at or near the northern limits of their range. Overall conclusions on the study areas are given. The exposed and semi-exposed west side of Jura was not found to have any area of particular merit, but the south and east coasts have been worked very inadequately and cannot be appraised. They are thought to be worthy of further attention due to their unusual hydrography. Loch Tarbert, on the west coast, was thought to be a good example of a shallow but intricate sea loch, with brackish upper part and two sets of current areas. However, lack of work carried out in the area did not make it possible to give a reasoned assessement of the loch shore, and it was graded at only 2/3. Further research there, was recommended, and might well result in an upwards revision of the grading. The north of Islay comprises rock platforms of more interest for their flora than their fauna, and the sediment areas around Loch Gruinart were very dull, affected by fresh water. The very exposed cliffs and rock platforms of the Atlantic west coast were found to be of considerable merit, and at least of equal interest to any other similar areas, with diverse fauna and flora, and some rare species at the extremes of the ranges. It was assessed at Grade 1. The Oa was found to be less interesting at Grade 3, with less variety of rock formation and habitat. Also Grade 3 was Loch an t-Sailein, a mixed sheltered shore with little tidal range, and good representative diverse flora and fauna. Loch Indaal and the south and east coasts were found to be rather ordinary.