Clinical trials are important to the advancement of medical science. They provide the experimental and statistical basis needed to determine the benefit of diagnostic and therapeutic agents and procedures. The more patients enrolled in a clinical trial, the more confidence we can have in the trial's results. However, current practices for identifying eligible patients can be expensive and time-consuming. To assist in making identification of eligible patients more cost effective, we have developed a system for translating the eligibility criteria for clinical trials to an executable form. This system takes as input the eligibility criteria for a trial formatted as first order predicates. We then map these criteria against concepts in a target database. The mapped criteria are output as an Arden Syntax medical logic module using virtual medical record queries in the curly braces. The system was able to successfully process 85 out of 100 trials attempted. From these 85 trials, the system idendified 1,545 eligibility criteria. From these criteria, we generate 520 virtual medical record queries, 253 of which were deemed useful in helping to determine eligibility.