The common borage, Borago officinalis L., is of Euro-Mediterranean origin, but is found extensively in the wild. It is also cultivated as a garden plant, crop vegetable, or pharmaceutical herb. Analysis of random amplified polymorphic DNAs (RAPDs) revealed high levels of genetic diversity among 10 borage wild accessions and seven cultivars, which included five white-flowered selections grown in northern Spain for petiole production, and two blue-flowered lines used medicinally. These latter two cultivars and populations, sampled far from the original habitat of the species, were closely related to wild borage populations from northern Europe. The two medicinal cultivars did not differ from each other, while those used for petiole production differed significantly from their Spanish wild relatives. Differences among the 17 populations accounted for 41.4% of the total genetic variability; this value increased to 50.8% when only the 10 wild populations were considered. Population differentiation and within-population variability are discussed in relation to mating system, selection, and conservation practices.