We will conduct a pilot study to investigate the ability to generate a dose-response curve of serum 25-hydroxyvitamin D to incidental ultraviolet light exposure measured objectively with a computerized personal ultraviolet light radiation dosimeter among 10 healthy volunteers in New Mexico where the population is highly exposed to solar UV radiation. During the follow-up period we will collect solar exposure data through a self-reported sun exposure diary, in tandem with objective UV dosimeter data, and will collect blood samples for serum measurements. We will carry out clinical measurements of serum vitamin D, parathyroid hormone, and calcium and phosphorus ions. We will analyze the correlation between the vitamin D and the recorded UV exposure in order to evaluate physiological changes due to solar exposure. This pilot study is important for melanoma prevention as there is currently confusion among the public as to how much sun is needed for vitamin D production and when too much sun exposure will increase risk for developing melanoma.