Cancer has surpassed heart disease as the leading cause of death in the United States. The mortality rate for cancer is high (roughly 42%), and it increases dramatically with increasing age, especially in patients between the ages of 40 and 60 years old. Currently, the efforts at cancer prevention have been minimal. The drugs developed so far are expensive and have serious side effects. There are at least 18 vitamin D-sensitive cancers. Ultraviolet light, and specifically ultraviolet B (UVB), could reduce cancer by the limited exposure of suitable skin areas to UVB of an intensity and duration insufficient to produce skin cancer. An irrational fear of skin cancer is preventing this idea from being implemented. Though skin cancer incidence is significant, mortality from skin cancer is relatively rare. Roughly 1,000,000 Americans will be affected by skin cancer but only 10,000 deaths are expected in 2005 (a 1% mortality rate). Skin cancer is easily detected and often cured by excisional biopsy alone. Current practice among practicing clinicians is to use a prescription drug substitute for UV light, calcitriol (1-25 dihydroxycholcalciferol). However, high levels of (calcitriol) are dangerous, and there is no consensus on just what a high dose or a safe dose is. Apart from skin cancer, UV light exposure possesses few risks. Additionally, a number of botanical agents such as ginkgo biloba, vitamins E and C, carotenoids, selenium and proanthocyanidins can prevent the risk of skin cancer. Ginkgo biloba also possess the following additional cancer chemopreventive qualities: (1) promoting apoptosis of cancer cells; (2) an anti-clastogenic effect on chromosomes by repairing and reconstituting broken and damaged chromosomes; (3) a powerful therapeutic effect on the treatment of fibrosis-related cancer; (4) a therapeutic effect on free radical-induced cancer; (5) a therapeutic effect on the treatment of cancer incident to the result of numerous carcinogens; (6) a therapeutic effect on preventing free radical-induced cancer; (7) an enhancing effect on radiation therapy in the treatment of cancer; and (8) a therapeutic effect on reducing the size of cancer tumors. Ginkgo biloba is widely-used and has few adverse effects. The proposed preventive treatment for cancer consists of short intermittent exposure of the least sensitive areas of the body to sunlight and/or artificial ultraviolet light. The routine testing of plasma vitamin D levels help monitor the effectiveness of the treatment and periodic checkups with a dermatologist help monitor the safety.