Non-randomized clinical trial is the clinical trial in which the series of consecutive patients receive a new treatment and those which respond (according to some of the pre-defined criterion) continue to receive it. Those patients who fail to respond receive an alternative, generally the conventional, treatment. The two set of groups are then compared on one or more results variables. One of the problems with such type of a procedure is that patients who respond might be healthier than those patients who do not respond, possibly resulting in an obvious but not real advantage of the treatment.