Abstract Experiments were carried out on 11 species of Alyssum of which 9 had the capacity to accumulate very high concentrations of nickel. These hyperaccumulators were grown in substrates containing 30–10000 μg/g nickel. Their nickel content after 6 weeks was a function of the nickel content of the soil and reached a limiting value of approx. 10 000 μg/g in dried leaves of the 9 species. The tolerance of 4 of the species towards nickel was determined by measuring the length of new roots on excised seedlings suspended in aerated solutions containing 0–100 μg/ml nickel. Four hyperaccumulating taxa tolerated nickel concentrations in the range 15–60 μg/ml. In rate-of-uptake experiments on A. euboeum, it was observed that nickel uptake was complete in approx. 6 days after addition of nickel to the substrate.