AbstractThe use of properly controlled clinical trials in medical experimentation has been of vital importance to the progress of medical science. At the same time, the new form of experimentation has also generated some of our most difficult and perplexing moral dilemmas. The solutions to the many complicated ethical problems involved in human experimentation are not straightforward, and despite numerous books, articles, codes, guidelines, and declarations, many specific issues of right and wrong in human experimentation have not yet been definitively resolved. Society today has an obligation greater than ever to control, regulate, and enforce properly balanced codes of human experimentation in order to minimize the unacceptable ethical problems and maximize the desired results of moderm human experimentation. These, however, are not sufficient. The patient's greatest safeguard in experimentation is a skillful, intelligent, and conscientious physician and investigator. Thus, the investigator bears great responsibility in balancing between the common good and the individual's rights. In this article the relevant secular and Jewish ethical principles and rules concerning human experimentation are specified and methodologically organized. Particular emphasis is placed on the elucidation and evaluation of the ethical controversies surrounding randomized clinical trials.