Early radiation dermatitis develops after large doses of X-radiation. Inflammatory erythema develops within about a week. This may heal with desquamation and pigmentation. If the dose was high enough, painful blisters may develop at the site of erythema. In that case, healing usually takes place with atrophy, teleangiectasia, and irregular hyperpigmentation. Subsequent to very large doses, ulceration occurs, generally within 2 months. Such an ulcer may heal ultimately with severe atrophic scarring. Chronic radiation dermatitis occurs from a few months to many years. The skin shows atrophy, teleangiectasia, and irregular hyper- and hypopigmentation. Ulceration may be seen within the areas of atrophy. Radiation ulcerations should be studied by biopsy if they have been present for three or more months. After a long latent period, various malignant neoplasms may form. Most frequent is the basal cell carcinoma, followed by squamous cell carcinoma.