The performance of a two-stage evaporative cooling system was monitored in a residence in Scottsdale, AZ, in the summer of 1987. Two separate periods were monitored. In the first, the unit was operated as a singlestage, direct evaporative cooler, yielding an average 74 % of the wet-bulb depression. During the second period, the unff’s full capacity as a two-stagevaporative cooler was tested. The first stage, the indirect evaporative cooling process, reached an average 54% of the wet-bulb depression. The second stage of direct evaporative cooling yielded an average 88% of the wet-bulb depression. In general, the supply dry-bulb air temperature was below the wet-bulb temperature of the outside air. The maximum indoor temperature recorded was only 85. 7°F, with an average temperature of 79.5°F. Regression models predicting supply air temperatures were derived by using outdoor dry-bulb and wet-bulb temperatures as independent variables.