Abstract: The present invention relates to a topically applicable formulation containing Valproic Acid or a derivative thereof which can be used alone or in combination with topically applicable formulations of retinoids or of nuclear receptor ligands, or of chemotherapeutic agents (e.g. 5-Fluorouracil). The formulation is useful for the topical treatment of cancerous skin disorders, such as Basal Cell Carcinoma, Squamous Cell Carcinoma, Keratoakantoma, Bowen Disease, cutaneous T-Cell Lymphoma and also for the topical treatment of pre-malignant lesions, and of inflammations of the skin and/or mucosa. The invention also relates to the use of this topically applicable formulation for the protection from UV light and for the treatment of sun burn. The invention includes the use of VPA for the manufacture of a clinically used medicament for the topical treatment of the human diseases listed above.