An essential place in the modern structure of the pharmaceutical market belongs to drugs: biotechnological products of various origins. These drugs, such as recombinant insulins, interferons, interleukins, erythropoietin, and so on, are essential to patients’ lives. At the same time, statistical data on introducing these drugs on the market and several low-molecular drugs demonstrate that they are insignificantly more effective than a placebo. For example, the use of beta-interferon (in the treatment of disseminated sclerosis) exceeds the placebo in effectiveness by only 8 % (placebo: 30%; beta-interferon: 38%). The situation is almost the same for low-molecular drugs such as antihypertensives. The effectiveness of amlodipine at the third stage of clinical tests was only 22% higher than that of the placebo (amlodipine: 52%; placebo: 30%). The reasons a drug might be ineffective or of little effect for 48% of patients have not yet been determined. The most difficult to explain is the ineffectiveness of drugs whose acceptors are cell receptors that have long been the study subjects, namely, adreno-, choline-, and histamine receptors. It remains a mystery why the same drug can be ineffective for one group of patients while remaining practical for another. Due to this little-studied peculiarity of the human organism, most antihypertensive drugs are combined. It is especially necessary to combine at least three drugs with different mechanisms of action but the same result: antihypertensive or cytostatic. In the latter case, the differences between various kinds of tumors are specially marked in sensitivity and the individual peculiarities of a specific tumor and host organism. Even polychemotherapy often turns out to be ineffective in the treatment of patients with cancer. The FDA’s depressing statistics on the third stage of clinical tests of drugs demonstrate the low effectiveness of practically all medicinal drugs available on the pharmaceutical market. The average efficacy of the most potent drug (morphine) is 75%. In other cases, we observe intolerance and toxic effects or an opposite reaction. Even in narcotic drug applications, only 60% of the people who took them are observed to experience the classical impact. The other group of people who took, for example, cocaine suffered a severe headache and dizziness without any signs of anesthesia. This kind of divergence of effects may be caused by polymorphism of the receptor system within the human population. Earlier, the structure of receptors was considered to be absolutely conservative and invariable for a single, or sometimes several, animal species. At present, more and more scientists tend to believe that receptors differ in much the same way as human faces, even within a single species. These differences are caused not only and not so much by the change of the primary amino acid sequence of receptors’ protein base but also by conformation changes of secondary and tertiary structures. Although they are formally similar in primary structure and molecular weight, different people’s receptors are actually different combinations of protein isoforms. This is especially apparent in the example of a major histocompatibility complex (MHC) antigen isoform combination. The selection of this complex is vitally important to organ transplantation processes. If thousands of variants and combinations exist for the MHC system, why should the structures of an organism’s other receptors be conservative within a species? Most likely, similarly to MHC antigens, the tertiary structures of the majority of cell receptors differ significantly by isoform profile within a population. This hypothesis provides a good explanation for drugs’ low levels of effectiveness. A conservative structure of a classical drug (like one“key”) cannot match a specific receptor (“many different, though similar, locks”) in all individuals of one species equally and with equal affinity.