Radon levels and radioactivity were measured in 50 shops and storage areas for building materials in Sudan. Charcoal canister and gamma spectrometry systems were used to measure radon in 55 types of natural material, and concentrations of 71–292 Bq/m³ (mean, 154 ± 38 Bq/m³) were found. The concentration of radium (²²⁶Ra) ranged from 2.8 to 182.5 Bq/kg, of thorium (²³²Th) from 1.2 to 302 Bq/kg and of potassium (⁴⁰K) from 82.3 to 1413.3 Bq/kg. Porcelain, ceramic and marble showed high values, while gravel types had low radioactivity. Radium in building materials was well correlated with radon (r² = 0.77). The average annual dose of workers at these sites due to inhalation of radon was estimated to be 2.8 mSv. The activity index of building materials ranged between 0.33 and 1.97 (mean, 0.77).