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The uptake of c a d m i u m by the roots of plants, and its transport to shoots was examined using solution culture. U p t a k e by the roots of perennial ryegrass over a period of 4 hours from an aqueous solution containing 0.25 p p m c a d m i u m as CdC12 was (i) enhanced by killing the roots and (ii) depressed when Ca 2÷, Mn 2* or Zn 2+ were added to the solution. The distribution of c a d m i u m between the roots and shoots of 23 species was examined at 4 days after a single, 3-day exposure to a nutrient solution containing 0.01 p p m added Cd. I n all except 3 species, i.e. kale, lettuce and watercress, more t h a n 50 per cent of t h a t taken up was retained in the roots. The concentration in the roots was always greater t h a n in the shoots, and in fibrous roots of fodder beet, parsnip, carrot and radish it was greater t h a n in the swollen storage roots. W h e n perennial ryegrass was similarly exposed to solutions containing 0.01, 0.05, and 0.25 p p m added cadmium, uptake, as measured at 3 days after adding cadmium, increased with increasing rates of addition, b u t the proportion retained in the roots was constant (approximately 88 per cent). There was no further transport from roots to shoots during the next 21 days, with the result t h a t the concentration in the shoots decreased progressively with increasing growth. I t is concluded t h a t although the roots of several species can take up large quantities of c a d m i u m from solution there are mechanisms which m a y restrict the m o v e m e n t of c a d m i u m through plants, and thus to animals.