Video-microscopy is a video-imaging system which permits direct visualization of the skin surface and capillaries, by using a microscope attached to a camera, a video-recorder and a printer. This technique provides information on the morphology of capillaries in vivo and has been used both for research into normal skin microcirculation and as a clinical method to detect capillary changes in psoriasis and other skin diseases. The aim of this study was to evaluate the morphology of capillaries in psoriatic plaques before and after treatment with tacalcitol, a new topical vitamin D3 analogue. Clinical evaluation was made after 3 and 6 weeks of therapy. After 3 weeks a reduction in erythema and scaling was noted; and areas in which capillaries were less tortuous became evident. After 6 weeks, capillaries were less dilated and tortuous in the whole plaque and had lost the large and tortuous appearance of active psoriasis.