Overt iatrogenic cutaneous atrophy is easily recognized; however, the earliest signs of such an adverse event may be covert. Preatrophy is proposed as a term to describe the subtle unmasking or normally covert subpapillary vascular channels found by the use of enhanced skin surface magnification techniques. We conducted a randomized double-blind, bilaterally paired comparison clinical trial in patients with chronic plaque psoriasis treated with twice-daily (nonoccluded) superpotent topical steroids for 2 weeks. Occult reversible delicate networks of horizontally oriented vascular channels were found within and surrounding 20% (23/118) of the involved psoriatic plaques during the course of the study. The use of a hand-held magnifying lens (8X), mineral oil, a coverglass, and adequate illumination allow recognition of preatrophy. Preatrophy was more frequently found in women than in men.