Biomonitoring of workers and communities raises important legal and ethical concerns, but the two contexts are different. Monitoring workers is usually done by, or at the instigation of, the employer who, in law, is responsible for their health and safety. Whenever worker monitoring leads to the removal of workers, difficult issues emerge affecting labor-management relations, labor law, and discrimination law. Resulting legal and ethical questions are usually framed with the context of the employment contract or labor relationship. In contrast, public health or environmental officials may be the driving force behind biomonitoring of the community. No employer-employee relationship exists, and the doctor-patient relationship may be tenuous. The community may often request biomonitoring, but the situation is no less contentious. On the basis of an historical view of monitoring events within the US, mechanisms are suggested to promote positive interactions between employers and workers and among agencies, individuals, and groups in the monitoring of chemically contaminated communities.