If you're really lucky you can find data at clinicaltrials.gov. For most completed studies there are no results reported, though. You will probably find this Ted talk interesting about the under-reporting of negative results from clinical trials: https://www.youtube.com/watch?v=RKmxL8VYy0M

Did you check on "Clinical trials.gov" website? Another option is to look for that specific investigator who has been working on similar topic and publishing. If you are working on cancer research and looking for clinical trial data, probably, ASCO, AACR annual meeting abstract books are additional tools.

You can find the clinical trials data at International Clinical Trial Registry Platform Website.

Thanks to all of you, the answers really help. TED talk is interesting and clinicaltrials.gov seems to be very useful. My problem is, that I find only the human trials and not corresponding animal trials or vice versa.

In these situations, I do another search in same data bases (PubMed, Web of Science, ASCO, AACR etc) for the same authors and look for pre-clinical data or in vivo animal models of the diseases that I study. Most of the time, I do get useful information.

It depend what you are looking for

The Yale University Open Data Access (YODA) Project

http://medicine.yale.edu/core/projects/yodap/datasharing/index.aspx

Data from Alzheimer’s disease Neuroimaging Initiative (ADNI) are available to researchers worldwide:

http://www.adni-info.org/Scientists/ADNIData.aspx

Anonymized sample medical image datasets from different trials are available from

http://wiki.na-mic.org/Wiki/index.php/Downloads

You can check

www.clinical trials.gov

But if you need to formulate clinical trial you should have like brain storming with group interested in the subject to come with an original idea

Thanks Mohamed. I need old data to compare the results of animal trials with human trials.