The greatest legal impact of medical screening and biological monitoring may be in proceedings to compensate workers for occupational disease. In workers' compensation, failure to demonstrate a disease's work-relatedness has often barred compensation. Screening and monitoring data can add a new causal link by demonstrating longitudinally a worker's reaction to a toxic exposure. Employers may also use the data to rebut claims. In tort suits, the data can help establish causation and aid the admissibility of expert testimony. Of most significance, it may create a higher legal standard of care for employers based on increased knowledge of their workers' health status, which may open up new grounds for suits. These legal implications of greater liability may make employers reluctant to collect medical test data. On the other hand, testing programs may aid them in legal proceedings by demonstrating good faith efforts to reduce disease risks.