Increases in metal element concentrations in the water washings from lichens previously subjected to stress are often used as a measure of membrane damage. Experiments involving the release of elements from discs of Pel tigern horizontalis, exposed to either desiccation or heavy metal stress, are used to test the validity of this approach. A sequential elution procedure can be used to assay the actual losses from the intracellular fraction. The importance of knowing the proportion of the elements in such intracellular material available for release is discussed. The ratio of intracellular K and Mg released is used to consider whether membrane damage is generalised or specific to one element