Abstract: A method and apparatus for monitoring optical radiation which, in a preferred embodiment, takes the form of a biologically weighted ultraviolet radiant energy monitor which provides a direct indication of the hazards to humans from the ultraviolet radiant energy emanating from the optical radiation source being monitored. The source of radiation is first spectrally dispersed by passage through a suitable prism or diffraction grating. Portions of the spectrally dispersed radiation are mechanically masked in accordance with a predetermined biological weighting. The subsequent weighted output from the mechanical mask is then fed to a suitable detector. In the various embodiments of the ultraviolet hazard monitor, a quartz prism or diffraction grating spectrograph is utilized to spectrally disperse the incident radiation spatially and a plate coated with sodium salicylate or other suitable converter is placed in the exit plane of the spectrograph.