Abstract: AIM To investigate the effect of clopidogrel on nailfold microcirculation (NM) in patients with stable coronary artery disease (SCAD). METHODS A retrospective cohort method was used in this investigation. One hundred and thirty-five SCAD patients were recruited and divided into two groups according to their administration of clopidogrel in the last 3 months:patients taking clopidogrel (n=61) and patients not taking clopidogrel (n=74). Nailfold capillaroscopy was performed for each patient and the abnormal grade and evaluation score of 11 indicators of NM were compared between the two groups for the effect of clopidogrel on the NM in SCAD patients. RESULTS NM total scores in patients taking clopidogrel were significantly lower than those in patients not taking clopidogrel (P<0.01), which was mainly caused by decline of the flow score and loop-week score (P<0.01, P<0.05). The differences of morphology score and between the two groups were not significant. Both the proportions of moderately and severely abnormal NM were lower in patients taking clopidogrel, while the proportions of normal and mildly abnormal NM were higher than those in patients not taking clopidogrel (P<0.01). Overall differences of the abnormal degree of NM between the two groups was significant. Patients taking clopidogrel had a lower degree of erythrocyte aggregation compared with that in patients not taking clopidogrel (P<0.05), but no significant difference was found in other indexes of NM between the two groups. CONCLUSION Clopidogrel may improve the NM abnormality of SCAD patients related to its role in reducing erythrocyte aggregation. However, this conclusion should be further proved by additional prospective and large sample randomized controlled studies.