Traditional tort law does not allow a victim of exposure to a toxic substance to seek damages without evidence of actual loss. Given the difficulty of collecting damages after a long latency period, however, we examine the desirability of granting exposure victims an independent cause of action for medical monitoring at the time of exposure. We show that such a cause of action is not necessary to induce victims to invest in efficient monitoring. It can, however, increase incentives for injurer care, but only at the cost of greater litigation costs. The general reluctance of courts to adopt a cause of action reflects their recognition of this trade-off.