Unknown Clinical Trials Unknown clinical trials lack detailed information as to their status, as well as other important updates. These trials are often international studies, though some are domestic. These trials are so called because the United States National Institutes of Health have not received up-to-date details on them. In some cases, significant periods of time have passed since the details of these trials have last been updated. Although not an official recruitment status the U.S. National Institutes of Health recognizes, it is, nevertheless, an important category to make mention of because these trials do exist. In many of these unknown clinical trials, the last known status was active, and further information was never given as to the results. Whatever is not known about these trials, it can be reasonably inferred that those without recent update did not produce exceptional results, or such information would have likely been conveyed to the U.S. National Institutes of Health.