Though Sudan is characterized by low seismic activity, several large earthquakes resulting in loss of life and damage to property have been recorded. The largest of these events, on 20 May 1990 ( Ms = 7.1–7.4) (Giardini and Beranzoli 1992) near Juba in the southern part of Sudan was probably the largest earthquake in Africa in the 20th century. Other earthquakes that caused major damage and even deaths include the Suakin graben earthquakes ( Ms = 5.8) of 12 May 1938, which were located in the western margin of the Red Sea; the Jebel Dumpier event located in Central Kordofan ( Ms = 5.6) (Qureshi and Sadig 1967), of 9 October 1966; and the Khartoum event ( Ms = 5.5) of August 1993. In 2001 the Geological Research Authority of Sudan (GRAS) established a seismic network to monitor earthquake activity in the region. The network is distributed around Khartoum for practical reasons, and local, regional, and distant earthquakes have been recorded. In this paper we describe the Sudan Seismic Network (SSN) and give an overview of the data recorded during the period from November 2003 to April 2006. These data were recently re-evaluated during a seismological workshop held at GRAS in April 2006 (Havskov 2006). Data recorded between network installation in 2001 to November 2003 are not available. The SSN consists of three long-period stations located in Khartoum State: Silate (SLAT), Merkhyat (MRKH), and Jebel Aulia (JAWL), at distances to the central station in Khartoum of 32 km, 23 km, and 42 km, respectively (figure 1). All equipment in the field and at the central station is provided by Lennartz. Each remote station consists of a long-period three-component seismometer with a frequency response between 0.05 Hz and 20 Hz, a MARS-88 basic data acquisition unit, and bidirectional radio-frequency (RF) …