Corporate data fall under the general category of administrative data and provide varied information on the worker and workplace. Studies of worker health, including evaluations of workplace programs, are often based on corporate data. With the exception of health care claims data, which are usually administered by a third party, the corporation collects these data and grants permission to use them. In light of new federal regulations, gaining access to corporate data is more complicated and intimidating than ever before. This paper discusses the impact of federal regulations on the use of corporate data in research, the potential of corporate data in evaluation studies, the challenges to obtaining and using these data, and finally, study designs that make use of corporate data.