The effectiveness of cathodic protection on the exterior bottoms of aboveground storage tanks is best measured with permanent zinc or copper-copper sulfate reference electrodes placed under the tank bottom. The use of these electrodes is preferable to measurements taken at the periphery of the tank since peripheral measurements do not reflect the potentials deep under the tank. The asphalt storage tanks were maintained at a temperature of about 350°F (175°C) to keep the asphalt in a liquid state. The temperature of the soil at electrode depth was about 300°F (150°C), too hot for the use of conventional electrodes. Corrosion measurement probes with high temperature cables were substituted. Zero corrosion rate as measured on the probe indicates effective cathodic protection. The probes could also be used as coupons for measuring polarized potentials. Keywords: aboveground storage tanks, asphalt tanks, cathodic protection, corrosion monitoring coupons, corrosion monitoring probes, high temperature cathodic protection monitoring, reference electrodes