Chemical  peeling involves  the topical  application  of a wounding  agent  with the goal of effecting an organized regeneration  of the skin. The histological features of photo aged skin include structural abnormalities that disrupt normal epidermal and dermal architecture. In the present prospective study we compared short and long term clinical and histological changes that occur after three sessions of enhanced medium depth chemical facial peel with 35% trichloroacetic acid on ten patients with photo aged skin changes. Biopsy specimens were taken pre-peel (control), and 3, 12, 48, months post-peel, for histological, and immunohistochemical analysis  to assess total collagen  type I content  throughout  the  study that  reach up to four years. Histological evaluations during the course of treatment have revealed an array of time­ dependent morphologic changes that were classified into early, intermediate, and late. Clinical resolution of actinic damage corresponded with restoration of epidermal and dermal polarity. Characteristic  histological  and immunohistochemical   analysis  post-peel  include  decreased elastic fibers, increased activated fibroblasts and organized parallel arrays of collagen fibrils. As  treatment  is  continued  beyond  12  months,  the  neocollagen  synthesis  and  organization continues to increase and elastosis continues to decrease. Besides, increases in epidermal and dermal mucin and decreases in epidermal melanin. We concluded that although there was no direct correlation between histological changes and clinical improvement, the major structural changes appear to be directed at restoring the skin to the pre-sun-damaged state.