For more than 15 years evidence has been accumulating that there is a link between a lack of melatonin and cancer, especially breast, ovarian and prostate cancer. For a similar period it has been known that exposing the eyes to light when melatonin is normally flowing reduces or eliminates the flow. What is relatively new is that it is primarily the blue wavelengths that are responsible for loss of melatonin. Blocking these blue rays with amber glasses restores melatonin flow. Also new is the direct evidence, from analysis of the famous nurses' health study, that having more melatonin present in first morning urine is linked to a reduction in the incidence of breast cancer. This leads to the hypothesis that wearing amber glasses (or using blue-free light bulbs) for a few hours before bedtime maximizes melatonin production and reduces the risk of breast, ovarian and prostate cancer and possibly other cancers.