Cryosurgery is an ablative therapy dependent on the sequential destructive events associated with tissue exposure to repetitive freeze-thaw cycles. Until recently, it has been thought that cell death was due exclusively to osmotic-related events, intracellular ice formation, and post-thaw ischernia resulting from vascular stasis. Due in part to the time temperature transitions that exist across the freeze zone it was presumed that intracellular freezing dominated within the proximal zone of the frozen tissue target while osmotic-related damage dominated distally. Experiments were designed using the prostate cancer cell line, C-3 as an in vitro model to study the effects of temperature on the molecular mechanisms underlying cell death. Confluent PC-3 cultures were exposed to temperatures ranging from 37 C to 80 C and allowed to recover for two days. Dead and living cells were isolated and assayed for DNA fragmentation using agarose gel electrophoresis. Cells exposed to temperatures above -15c exhibited non-random DNA fragmentation a characteristic of apoptotic cell death: whereas cells exposed to temperatures below -1 5c died primarily through necrosis as revealed by random DNA fragmentation. Cell viability was than assessed post-cold exposure with the non-invasive metabolic indicator. Alarnar Blue. Remarkably, an apoptotic inhibitor, IDN- 1529, which completely blocked aptoptotic DNA laddering following exposure to -10c and greater, also partially inhibited cell death in cultures exposed to temperatures ranging from -10 to -75c. This inhibition occurred even at temperatures at which necrosis appeared to be the primary cause of death. In summary it is concluded that (1) PC-3 cells can die either by apoptosis or necrosis and the mode of death is determined by the treatment temperature, and (2) apoptotic inhibititors inhibit cell death of PC-3 cells even in regimas that appear to be exclusively necrotic. This observation provides the basis for reassessing Our knowledge of and therapeutic strategies toward cryosurgery.