On 5 August 1989 an iceberg was observed some 250m from the Negribreen glacierfront (Storfjorden, east coast West Spitsbergen, 78°30,8’N, 19°30, 0’E) with a flat top covered with shingle. A breeding colony of Arctic Terns was found on top of the iceberg, numbering 50-75 pairs. The iceberg originated from the Negribreen where a strip of shingle was visible running several kilometers ’inland’ on the glacier. Near the glacier front some more pairs of terns were nesting on the place where the iceberg came from. The colony was there situated at least 5 km distant from the nearest land, on top of a steep, 7 m high, glacier face. The colony was simply split in two and the main part was now floating away. It is discussed that the position of the colony was very good regarding feeding conditions (high concentrations of zoo-plankton occur outside glaciers as a result from passive upwelling) and land predators such as the Arctic Fox, but rather risky in other respects. The iceberg was grounded and at the time of observation not in immediate danger of tipping over. The breeding of terns on glaciers (or icebergs), and the breeding of Arctic Terns in this part of Storfjorden, was previously unknown.