Ultraviolet radiation (UVR)-induced suppression of cutaneous cell-mediated immunity plays an important role in the development of photocarcinogenesis in the mouse and a similar role is suspected in humans. Cell-mediated immunity is readily tested in vivo by measuring the contact hypersensitivity (CHS) response to topically applied haptens. CHS in humans is usually determine clinically, with a subjective scoring system. However, these subjective scores cannot be statistically analysed. This paper compares four methods currently used to quantify CHS elicitation responses in humans. The data show that ultrasound images provide the most accurate and reproducible measurements of the clinically observed CHS response. We also demonstrate that assessment of the primary allergic response is a useful indicator of the magnitude of the elicitation response and can be used to avoid severe CHS reactions in volunteers. There are few human studies investigating the effects of solar simulated radiation (SSR) exposure on immunosuppression. In this study we demonstrate SSR is highly immunosuppressive in all subjects tested. Irradiating a small area of skin with a single exposure to 3MEDs of SSR completely suppressed CHS both locally (12/12 volunteers) and systemically (10/12 volunteers). Our data do not support a role for a genetic susceptibility to UVR-induced immunosuppression in humans.