To the Editor.— The article by Tucker et al (Archives138:77-79, 1978) may be used as a model by other medical centers for the development of an occupational health service. I believe it would be useful to emphasize a distinction between certain required and voluntary procedures. Tucker and coauthors report tetanus immunization as being a requirement for some groups. It should be strongly encouraged but in the absence of a specific legal mandate, one may encounter problems in enforcing it as a requirement, especially when the immunization is primarily for the benefit of the employee and failure to be immunized would not place others at risk. This may be compared with tuberculin skin testing or chest roentgenograms for tuberculosis control. Although the employee will benefit, the principal justification for making it a requirement is the protection of others, primarily patients but also fellow workers. In many jurisdictions the testing is