Plant material from three different species was artificially labelled by root uptake from solutions labelled with 137Cs activity. Measurements were made of 137Cs activity, pH and potassium content on the leachates from litter samples over a three-month period. Microbial activity was assessed by measuring the respiration rate of each litter sample. Rates of release of both 137Cs and K from 'Calluna vulgaris' litter were slower than those from 'Trifolium repens' and 'Agrostis capillaris', but the two elements had different release patterns. For 'T. repens' and 'A. capillaris' repeated drying and rewetting of the litter during the experimental period changed the pattern of 137Cs release when compared with continuously moistened litter samples.