The recognition in Skye of olivine tholeiite lava flows, with low alkali (1·7–1·9 per cent Na2O,0·04–0·14 per cent K2O) and high calcium (12·7 per cent CaO), is reported. An account of their mineralogy and petrology, seven major element analyses, some trace element data, and the results of one atmosphere melting experiments are presented. These lavas, quite distinct from the plateau lavas in Skye, are postulated as representing the early stages of a central cone volcano in S.W. Skye and thought to be closely related to the parental magmas of the Cuillins layered basic intrusion complex.