CCTV-microscopic observation of nail-fold microcirculation was made on 11 AIDS patients and 11 healthy European adults. Unique severe microcirculatory disturbances were observed in these patients: (1) severe dysfunction of automatic alternative capillary blood flow perfusion. All the capillary loops in the same microscopic field emptied at the same moment and remained empty for a long time (3-100 seconds). Subsequent filling up of the capillary loops was very slow (1-2.5 min/loop). (2) remarkable damage of endothelial cells in the capillary wall. Some parts of the capillary wall were penetrated by some heterogeneous, visible and sludgy mass, making the wall swelled and the lumen narrowed. The wall tension in all the capillaries was markedly decreased. After the capillary loops had emptied, these damaged parts of the wall still remained in the field. These findings demonstrated the deep involvement of microcirculation in the pathogenesis of AIDS, and also showed the close relationship between microcirculation and the immune condition of the organism.