The recent boom in underwater exploration and archaeology has led to an enormous increase in the recovery ofmetals from wrecks in the form of objects, coin and ingots. Of course this area of exploration has always attracted great interest and indeed most early divers, such as the famous Dutchman, Jacob Johnson, 'Jacob the diver', who worked in the early 17th century, as well as most early developments in diving were spurred on by the prospect of metals beneath the waves. The accelerated rate of discovery and recovery has been brought about by new techniques and equipment making it possible to work underwater much more easily and at much greater depths than was hitherto feasible. Although much of the interest is still unashamed treasure hunting for financial gain, other, more scholarly, interest is also being focussed on material, such as ingots from wrecks which so often provide what equivalent land-based discoveries lack--a dateable context. This interest was recently underlined by the highly successful, and over-subscribed conference 'Seabourne trade in metals and ingots' jointly organized by M.A.R.E. and the CBA at Oxford on 16th-18th January 1987. The ingot material presented ranged evenly from the Bronze Age through to the 19th Century and attracted the participation not just of divers and marine archaeologists, but also of economic historians, prehistorians, metalurgists and even art historians. All found something of interest with the ingot material now coming from the sea in ever increasing quantities, often presenting new angles to their own special disciplines.The ingots are of course of prime importance for documenting long distance trade-the demand for metal was after all one of the chief stimuli to the development of trade. Their careful study and scientific examination is also providing notable information in other areas not strictly related to trade, such as early technology and art history.The British Museum has always collected ingot material along with other antiquities from the more remote past, and has now commenced a collection of ingot material from documented wrecks of the medieval and post medieval periods. This is part of the Museum's policy of collecting material relating to the production of metal through the ages. It is the purpose of this short article to bring this small but growing collection to the notice of underwater archaeologists. This is very much a beginning and advice and comments would be welcomed.First, we will describe some of the areas where ingots from documented wrecks are already providing valuable information. The analysis of metal artifacts, ingots included, from the past can give us a variety of information. The major metals show that alloys were available, and the trace elements can give some indication of the smelting processes and the degree of purity achieved in the refining of the metal. As well as this information on the contemporary metal technology, the analysis can sometimes be used to give some indication of the date of manufacture or the provenance of th...