The present study was designed to evaluate the biological and clinical significance of the expression of two different 
proliferation markers used for assessment of the proliferative response in different proliferative skin conditions, in comparison to normal skin. 
42 specimens were collected including 7 specimens of normal skin and 35 specimens representing different skin lesions 
diagnosed as verrucous vulgaris, chronic suppurative dermatitis, foreign body granuloma, squamous papilloma and basal cell carcinoma (7 specimens each). Prepared paraffin sections were subjected to Hx. and E and immunostaining to detect PCNA and a nuclear antigen reacting with Ki-67 monoclonal antibody. Morphometric assessment of the thickness of the epidermis and percent positive nuclear area using image analysis was performed and followed by statistical analysis of the data. A highly significant increase in the thickness of the epidermis was found in all proliferative conditions in comparison to normal skin. PCNA immunoreactivity was highly significantly increased in all proliferative conditions except in foreign body granuloma when compared to normal skin. Concerning Ki-67 immunoreactivity, a significant increase in the mean area percent of the positive cells was detected in skin affected by verrucous vulgaris and squamous papilloma and highly significantly increased in cases of basal cell carcinoma, when compared to normal skin. A highly significant difference between PCNA and Ki-67 immuno-reactivity was estimated in normal skin and in the different proliferative conditions except in basal cell carcinoma, where no significant difference was recorded. We concluded that, Ki-67 detecting a nuclear antigen might be more specific for evaluation of the proliferation rate in neoplastic lesions particularly malignant conditions.