Alterations in concentrations of intracellular free calcium ([Ca2+]i) were examined in mouse sarcoma S-180 cells exposed to cisplatin, mitomycin C and adriamycin, as related to cell viability. The [Ca2+]i was measured using the fluorescent Ca2+ indicator, fura-2. During the first 24 hr of incubation of the cells in vitro, in the presence of the drugs, the [Ca2+]i was lower than in the control cells. After 24 hr of incubation, the [Ca2+]i began to increase at a time when the cell viability was reduced to 50% of the controls, and finally exceeded 1 microM with reduction to 10%. The increase in [Ca2+]i was reciprocal to the loss of the cell viability. Changes in Ca2+ concentrations in the medium did not alter the results. These findings suggest that in the presence of anticancer drugs there is an accumulation of free Ca2+ with a release of this ion from internal stores and that cell death follows disruption in the homeostasis of intracellular Ca2+.