Because we were a residential Phase-I unit, the volunteers were controlled to a great extent, and we could be sure that we knew what is “added” to each volunteer and their base line “contents.” Other phases, especially the later ones, Phase II and Phase III, of drugs’ clinical development are not so well controlled, as these tend to be patient studies, and patient compliance with the protocol can become a significant issue. As I have had little or no real experience of these later phases of clinical trials I shall not develop any more discussion on the issue. I would however say that the general principles presented here do work in any situation, whether you are dealing with patients or volunteers; it is just that the details are different.