Selected average analyses of tholeiitic basalts, which have markedly differing contents of K2O, show a broad coherence between K, P, Ti, Ba, Rb, Sr, and Zr. The content of K2O in the average analyses of 43 tholeiitic provinces shows a wide range (0.07–1.61 per cent) and has a positively skewed frequency distribution. K2O in individual tholeiitic basalts and dolerites has a similar distribution pattern.