Abstract: Methods and apparatus for exposing a sample to ultraviolet radiation are disclosed. The present invention permits a sample contained within a shielded housing to be exposed to a source of ultraviolet radiation and simultaneously observed. The sample rests on a stage that can be moved relative to the source of the ultraviolet radiation while the irradiation is taking place, thus the effects of ultraviolet radiation upon biological materials such as blood can be determined. In a preferred embodiment, upper and lower banks of ultraviolet bulbs are disposed on either side of the stage. The movement of the banks of bulbs and the stage relative to one another is preferably controlled by a set of lead screws. In certain embodiments, the intensity of the emissions of the bulbs themselves can also be altered while continuously observing and irradiating the sample.