In our study, we retrospectively evaluated the vitamin D levels in the form of 25-OH D of skin cancer patients, patients with precancerous skin lesions such as actinic keratosis, and healthy individuals, and also aimed to investigate the interrelation of vitamin D and redox parameters such as erythrocyte GSH content and catalase activity, plasma TBARS, carbonyls and TAC levels in those patients. The gene discussed is CAT; the disease is skin neoplasm.