By studying the effects of four concentrations of cadmium (0.25, 2.5, 25, 250microM) on Pisum sativum L. roots, we compared parameters generally used in short-term tests for environmental monitoring - root length, mitotic index, occurrence of mitotic aberrations - with less explored parameters related to meristem activity, such as apex size and viability, percentage of DNA-synthesizing cells and microtubule alterations. The results show that low cadmium concentrations caused a reduction of root growth, which is directly related to reduction of apex length, mitotic activity and percentage of DNA-synthetizing cells. The microtubular cytoskeleton was highly sensitive to cadmium, as microtubule alterations appeared after treatment with the lowest cadmium concentration, pointing to microtubules or microtubule-associated proteins, among the main targets of cadmium. In contrast, cell viability was a less sensitive parameter, as it decreased only upon treatment with the highest cadmium concentrations. The different sensitivities of the parameters examined in this work support the use of different endpoints for assessment of risk from polluted soils and waters.