Meteosat-derived hourly solar direct normal irradiances are compared to high quality ground measurements. For validation purposes the region of the Arabian Peninsula is selected due to its high solar energy potential and due to the availability of accurate ground measurements of the beam irradiance. Hourly ground data for the complete year 2000 are evaluated by automated and visual quality checks. Eight of 12 measurement sites fulfil the quality requirements and can be used for the validation purposes. The relative mean bias error, averaged over all 8 sites, is 4.3% for all-sky conditions. The relative root mean square error, averaged over all sites, decreases from 36.1% for hourly values down to 8.1% for the yearly sum. With this accuracy the method may well be applied for solar energy resource assessments in comparable regions and for detailed solar power plant simulations. Analysing one year of data of the Arabian Peninsula results in a maximum direct normal insolation of about 2650 kW h/m(2) in the north-east near Tabouk, while the minima can be found in the Al Soodah mountains with approximately 1650 kW h/m(2). (C) 2003 Elsevier Ltd. All rights reserved.