In response to a request from three California unions to evaluate potential health hazards from the use of video display terminals (VDT's) in information processing applications, the National Institute for Occupational Safety and Health (NIOSH) conducted a limited field investigation of three companies in the San Francisco-Oakland Bay Area. A preliminary walk-through survey was conducted in November 1979, followed by an additional four-phase, in-depth investigation in 1980, which used (1) radiation measurements; (2) industrial hygiene sampling; (3) a survey of health complaints and psychological mood states; and (4) ergonomics and human factors measurements. The radiation surveys indicated exposure well below current occupational exposure standards. Air samples showed no hazardous chemical exposures. A questionnaire survey indicated that a higher percentage of VDT operators reported more visual complaints at two of the three sites, more muscular complaints at one site, and more emotional complaints at all sites. Ergonomic evaluation indicated measured illumination levels at VDT workstations were generally acceptable, although problems of glare and physical dimensions of the workstations were sometimes noted. The report of this study provides detailed explanations of methodologies, tabulated results, general recommendations, and a 3-page reference list. Author/LMM)