FOR several years there has been controversy about the ages of the Uganda basement gneisses. Potassium–argon ages of micas from the basement rocks1 range from 600 to 415 m.y. whereas results for the apparently unconformably overlying Karagwe–Ankolean and Buganda–Toro sedimentary systems2,3 to the south (around the north end of Lake Victoria) suggest an older age limit of ∼ 2,000 m.y. for the underlying basement rocks.