I have tested a new source of ultraviolet radiation1 and have found it to furnish adequate intensity for the diagnosis of tinea capitis by fluorescence. In addition, it possesses several advantages not heretofore available. It is light, compact, durable and easily transported in the pocket. It consists of a single unit, roughly cylindrical, approximately 2 inches (5 cm.) in diameter and 10 inches (25 cm.) in length, containing the transformer in the handle and weighing only 19 ounces (570 Gm.), including the electrical cord and plug. Its radiation is concentrated almost entirely at 3,660 angstrom units, thereby eliminating the dangers of radiation in the therapeutic range. The lamp requires only a momentary "warming-up" period before reaching its maximum intensity, remains cool in use, does not go out if jarred or jolted and can be immediately relighted without an interval for cooling. The burner is reputed to have an exceptionally long