Photodynamic therapy (PDT) has both direct cell and indirect vascular effects. Both are well established and the latter has given rise to specifically target angiogenesis in PDT treatments. While the vascular effects are well understood, further advances in antiangiogenesis require a detailed understanding of PDT effects at the microvasculature level. Although some of the earliest investigations of PDT noted effects on platelet aggregation the importance of their interaction with endothelial cells and the crucial role of various signaling pathways is only now emerging. This review aims to give a general overview of PDT related studies on platelets, vascular effects, and their interaction with endothelial cells to indicate the potential for studies in this area. ; PUBLISHED ; This work was supported by grants from Science Foundation Ireland (SFI P.I. 09/IN.1/B2650 and P.I. 05/FE1/B862) and the Health Research Board (HRB Translational Research Award 2007 TRA/2007/11).