Alyssum bracteatum is the first Ni hyperaccumulator reported from serpentine soils of western Iran. In this study, uptake and accumulation of Co by a serpentine and a non-serpentine population of this species were tested under controlled conditions. Seedlings of A. bracteatum were grown in different concentrations of Co (0, 2, 5, 10, 15, and 30 mg Co L^-1) in solution culture (perlite) for 21 days. Tolerance to Co of serpentine population seedlings was significantly greater than the Co tolerance of seedlings from the non-serpentine population. Analysis of shoots and roots showed that the concentration of Co in both populations of A. bracteatum increased with increasing Co in solution culture, but amounts of Co in the shoots of non-serpentine plants were significantly less than those in serpentine plants. Plants of the serpentine population contained as much as 1830 µg Co g^-1 dry weight when grown in 15 mg Co L^-1 conditions, showing that this species is capable of hyperaccumulating Co under solution culture conditions.