Quantitative assessment of skin perfusion has value in both medical and surgical therapeutic decision-making. We have adapted a technique using intradermal xenon-133 dissolved in saline for use with a gamma camera interfaced to a mini-computer. It allows rapid evaluation of several sites simultaneously. The monoexponential washout rate of the injected tracer during the first 6 min is entered into the Schmidt--Kety equation to provide blood-flow rates in ml/min per 100 g. Reproducibility of the method in normal subjects is satisfactory. An important experimental variable is ambient temperature, since perfusion rates in normal limbs at low temperatures can approach those levels found in ischemic limbs. The intradermal technique has practical advantages over other methods for study of limb or skin perfusion.