Wind-tunnel tests were performed to investigate the spanwise drag variation commonly found on airfoils at low Reynolds numbers. Detailed spanwise measurements were taken to quantify this three-dimensional effect. Wind-tunnel test data are presented for both the E374 and SD6060 airfoils at Reynolds numbers from 200,000 to 500,000. The results show the effect of Reynolds number and angle of attack on the magnitude of these spanwise variations. Moreover, the measurements depict periodic trends in the profile drag and a relationship between the airfoil upper surface contour, the formation of large spanwise structures thought to originate at the laminar separation bubble, and the formation of the downstream wake.