Marine litter is becoming a significant contributor to marine pollution in the Western Indian Ocean. The litter comes in myriad forms, and from a diversity of sources. It includes waste from legal and illegal dumpsites located on the coast or on river banks; rivers and floodwaters; industrial outfalls; discharge from storm water drains; untreated municipal sewage, and littering of beaches and coastal picnic sites/eating areas. Waste dumped from shipping and port activities, and waste that is transported from distant marine locations through ocean currents, is also a contributor to the region’s marine litter load. Synthetic/plastic litter and similar persistent solid waste particularly damage the environment, degrading its ecological, economic, cultural, recreational and aesthetic value. In recognition of the problems caused by marine litter, a United Nations General Assembly resolution in November 2005 called for national, regional and global actions to address the issue. The United Nations Environment Programme (UNEP), through the Global Programme for Action for the Protection of the Marine Environment from Land-based Activities (GPA) and the Regional Seas Programme, is active in raising awareness about the marine litter problem. One of UNEP’s activities has been to commission this report_x001f_— a preliminary assessment of the marine litter problem in the Western Indian Ocean (WIO) region. The study was undertaken under the auspices of UNEP-GEF WIO-LaB Project entitled ‘Addressing land-based activities in the WIO region’ and coordinated by the Western Indian Ocean Marine Science Association (WIOMSA). The study aimed to collate the existing information about marine litter in the WIO Region, use it to determine whether or not there is need for concern, and recommend a way forward with regard to its management in the WIO Region. This report synthesizes information and data presented in national reports of 8 countries that are signatories to the Nairobi Convention for the protection, management and development of the coastal and marine environment in the Eastern African region, supplemented by secondary information from published and unpublished sources.