The randomized control clinical trial has become the gold standard scientific method for the evaluation of pharmaceuticals, biologics, devices, procedures and diagnostic tests, having been successfully used in both therapeutic and disease prevention trials. This text is structured to address the fundamentals as the protocol for a clinical trial is being developed. A chapter is devoted to each of the critical areas of a protocol. The fundamentals described here are based on sound scientific methodology, statistical principles and years of accumulated experience. The new edition is revised and expanded, with the number of examples illustrating the fundamentals considerably increased.