The rate of cytolysis in osmotically stressed unfertilized sea urchin eggs was analysed using a version of the Johnson-Mehl-Avrami equation, and fit with high precision (r 2>0.90) if the data sets were divided into two sectors. The slow process was first-order but the Avrami coefficient,n, for the initial fast reaction was 7. Suspecting that this might be a peculiarity of cells which are primed for climactic behaviour, we examined the process in red cells, whose decay is known to be of first or lower order at low temperatures if protected from excessive osmotic stress. Human red cells subjected to ‘thermal shock’, in which osmotically stressed cells are cooled below +12°C, show a pattern almost identical to the stressed sea urchin eggs except thatn of the rapid process exceeded 10. Based on the geometrical implications of such a highn, we believe that this phenomenon reflects a stress failure in the cytoskeleton and has important ramifications in cryopreservation.