Background: Anatomic location and depth of ectasia of port-wine stains (PWSs) are important prognostic indicators when evaluating treatment options for patients. Videomicroscopy permits subsurface evaluation of PWSs, thereby allowing determination of the depth of the ectatic vessels. Objective: Our purpose was to determine whether location of PWSs corresponds to the depth of the ectatic vessels. Methods: Seventeen patients presenting for evaluation or treatment of PWSs underwent videomicroscopy with a Video Loupe 7EX microscope. Data were recorded by location of the PWS as a type 1 lesion (blobs or globular structures) corresponding to ectasia of the superficial capillary loops, a type 2 lesion (rings) corresponding to ectasia of the deeper horizontal plexus, or a mixed pattern. Results: PWSs in areas that typically respond well to laser treatment (V3, neck, and trunk) were more likely to have a superficial type 1 pattern. PWSs in areas that have a poorer response to therapy (V2, distal extremities) were more likely to have a deeper type 2 pattern. Conclusion: We found that patients with lesions in the V3 dermatome and on the trunk and neck have more superficially ectatic vessels, whereas those lesions in dermatome V2 and on the distal extremities have more deeply placed vessels. Further studies are needed to determine whether videomicroscopy can be used to preoperatively predict treatment results. (J Am Acad Dermatol 2001;44:948-51.)