Development and validation of a measure of individual differences in social comparison orientation (the Iowa-Netherlands Comparison Orientation Measure [INCOM]) are described. Assuming that the tendency toward social comparison is universal, the scale was constructed so as to be appropriate to and comparable in 2 cultures: American and Dutch. It was then administered to several thousand people in each country. Analyses of these data are presented indicating that the scale has good psychometric properties. In addition, a laboratory study and several field studies are described that demonstrated the INCOM's ability to predict comparison behavior effectively. Possible uses of the scale in basic and applied settings are discussed.