Background: Squamous cell carcinoma(SCC) on sun-damaged skin is a malignant neoplasm that evolves from its inception as squamous cell carcinoma in situ, which is commonly referred to as an actinic keratosis(AK) or Bowen's disease(BD). Objective: The purpose of this study was to determine whether there is a significant association between cutaneous SCC on sun-damaged skin and AK or BD in Korean. Methods: A total of 50 Korean patients with SCC on sun-damaged skin was enrolled in this study. The hospital charts and histopathological slides of the patients with SCC on sun-damaged skin diagnosed at Chungbuk National University Hospital from July 1, 1991 to March 1, 2001 were reviewed. We investigated the incidence of actinic keratosis and Bowen's disease and histopathological characteristics of actinic keratosis at the periphery or within the confines of cutaneous SCC. Results: Of the 50 cutaneous SCC cases on sun-damaged skin reviewed, 96.0% (48 out of 50) were found to have concomitant AK or BD at the periphery or within the confines of cutaneous SCC. The most common histopathological subtype of accompanying AK in the cutaneous SCC was the hypertrophic type. Conclusion: The 96.0% prevalence of concomitant AK or BD and SCC in our biopsy population suggests a strong correlation between these lesions. (Korean J Dermatol 2001;39(10) 1100-1106)