Critical thinking is defined as a basic skill for nurses which leads to the best performance based on the best existing evidence. Although acquisition of this skill is highly emphasized, still there is no single definition for it. considering importance of critical thinking in performing nursing clinical care, current study was conducted aiming at investigating critical thinking progressive trend among nursing students in a nine-year period using library approach. Methods: This systematic research was conducted by search in Magiran, Iran Medex, and SID databases within 2001-2011. The author used critical thinking and nurse as key terms and found 15 research papers to critical thinking in nursing students and three review papers. Also, some papers on critical thinking in medical and paramedical students in Iran were also searched, examined, and compared. Other data bases such as Elsevier and PubMed were also used for enrichment of the discussion. Discussion: In terms of historical trend, critical thinking in nursing students has shown no progress within ten-year period (2001-2011) and generally no progress was observed in critical thinking based on standard tests (Watson Glaser test and California critical thinking skills test and Cornell critical thinking test) in the research works conducted in various Iranian universities. This trend is not specific to nursing students and it was also observed in other medical and paramedical fields. It seems that various factors are involved in this situation including lack of identical definition of critical thinking, lack of appropriate tools for evaluation of critical thinking needed in clinic, lack of regular, comprehensive, and purposeful plan in teaching critical thinking, and ambiguity in aspects of critical thinking in the view of clinical instructors and trainers. It seems that aspects of clinical critical thinking and its teaching and evaluation methods are not detailed and clear in Iran. It is suggested that clinical critical thinking and its aspects are investigated from the perspective of clinical instructors so that all nursing faculties teach critical thinking based on a specified and organized plan.