Abstract: A portable diagnostic lamp is constructed as a pocket appliance for inspecting teeth by fluorescent excitation of a fluorescible material which has been applied to the teeth and gums. A lamp comprises a casing housing a small battery-powered incandescent bulb with a lens supplying a divergent beam of rays and a rectangular filter located before the latter, which filter comprises a blue color filter with a dichroic filter applied thereto. A folding and adjustable mirror is located above the bulb, in use of the lamp and the longer sides of the rectangular filter and a filament of the incandescent bulb are arranged parallel to the pivot axis of the mirror.