The invention generally relates to treating diseased nails, and more particularly to treating diseased nails using radiation and/or another form of energy to substantially deactivate the source of the disease. A nail treatment can be performed by a medical professional without the use of a dying agent or an exogenous chromophore, and the treatment can be effective at eliminating the source of the disease without subjecting a patient to adverse side effects or causing substantial unwanted injury to surrounding tissue.