The visual assessment of erythema induced by ultraviolet radiation (UVR) involves a comparison of the irradiated site with surrounding nonirradiated skin. By viewing the skin through plastic filters of varying shades of brown to simulate different degrees of pigmentation and under either incandescent or fluorescent lighting, we were able to examine the influence of pigmentation and illumination on the perception of erythema. Illuminating the skin with either light source at the same illuminance did not affect the determination of the minimal erythema dose (MED). Likewise, the range of pigmentation that may occur in Caucasian skin had little or no effect on the perception of the MED compared with white, untanned skin. However, when the skin was viewed through dark brown filters that approximate the absorbance of Negro skin, erythema was only perceived at sites that had been irradiated with more than about twice the MED.