As a medical review officer, or MRO, your responsibilities are to review test results from a lab that conducts drug testing on behalf of a company, an athletic competition, or a state organization, such as a department of transportation. Your duties are to analyze and verify the lab results, as well as help ensure its accuracy. You work as an objective party to attest to the sanctity of the process and describe the results to employers. When tests come back positive, you may perform further investigative work to determine whether there is a legitimate reason for a positive result.