Abstract: The changes of microcirculation of nailfold were observed in 104 patients suffering from connective tissue diseases （CTD）, and they were compared with 100 cases of control. Significant differences were observed between these two groups. In the CTD group. the common characteristic findings were dark-red colour of blood. lineal-muddy or muddy blood flow. blurring of capillary loops. narrowed top of loops. many of the capillary loops showing patterns of tortuosity, branching. wavelet or papilla. and the number of abnormal capillary loops being over 50％. with reduced speed of blood flow. increased blood aggregation and nodules of the loop-top. The above results suggested that there were marked morphological abnormalities of skin capillaries in the patients with CTD. In addition to the above-mentioned common capillary abnormalities, there were characteristic manifestations in each group of CTD. Such as: 55％ patients in systemic lupus erythematosus group had dilatation of the venous limb of the capillary loop: 40％ patients in rheumatoid arthritis group lost pattern of hair-pin; 26％ pa-tients in rheumatoid arthritis group and 63％ patients in Behcet’s syndrome group showed multiplication of the capillary layers; increase of caliber of the arterial limb of the capillary loops was seen in ankylosing spondylitis group. Four out of five in scleroderma showed dilatation of the venous limb of the capillary loops. 2 cases de-monstrated the presence of aneurysms. Dilatation of both of the capillary limbs was observ-ed in dermatomyositis group. It is suggested that the microcirculatory changes mention-ed above may be used as diagnostic indices for CTD and multi-system involvement.