Summary. We assess the current status of breeding seabirds and waterbirds on the still mostly unpopulated Eritrean islands, many of which had never previously been visited by ornithologists. In 2001-07 we surveyed 325 islands (93% of the total), of which 210 were found to harbour 21 breeding species of seabirds and waterbirds. We counted c. 150,000 breeding pairs and estimate the total number at c. 175,000 pairs. The following species or subspecies were found to have internationally important breeding populations, as the Eritrean islands support more than 1% of the regional population: Crab Plover Dromas ardeola (>8,000 pairs), White-eyed Gull Larus leucophthalmus (5,900 pairs), Greater Crested Tern S. bergii velox (2,200 pairs), Lesser Crested Tern Sterna bengalensis par (63,000 pairs), Bridled Tern S. anaethetus fuligula (30,000-35,000 pairs), White-cheeked Tern S. repressa (18,000 pairs), Brown Noddy Anous stolidus plumbeigularis (11,000 pairs), Brown Booby Sula leucogaster plotus (10,000 pairs) and Eurasian Spoonbill Platalea leucorodia archeri (c.300 pairs). Socotra Cormorant Phalacrocorax nigrogularis, previously reported in the Red Sea only as a rare vagrant, was observed in large numbers and is suspected to breed in the southern islands. Currently, the main threats to breeding seabirds are egg collection by local and foreign sea cucumber fishermen, and the occasional introduction of cats. We confirm that the Eritrean islands deserve the status of Important Bird Area and we identify 50 islands in need of special protection.