The System Usability Scale (SUS) has been widely used since its introduction in 1986, but its factor structure has been assumed to be unidimensional. However, factor analysis of two independent SUS data sets reveals that the SUS actually has two distinct factors: Usable (8 items) and Learnable (2 items). These new scales have reasonable reliability (coefficient alpha of .91 and .70, respectively) and correlate highly with the overall SUS (r = .985 and .784, respectively). They also correlate significantly with each other (r = .664), but at a low enough level to be used as separate scales. A sensitivity analysis using data from 19 tests showed a significant Test by Scale interaction, further supporting the differential utility of the new scales. Practitioners can continue to use the standard SUS as is, but can also benefit from these new scales to extract additional information from their SUS data. The data also support the use of "awkward" rather than "cumbersome" in Item 8.The System Usability Scale (SUS) has been widely used since its introduction in 1986, but its factor structure has been assumed to be unidimensional. However, factor analysis of two independent SUS data sets reveals that the SUS actually has two distinct factors: Usable (8 items) and Learnable (2 items). These new scales have reasonable reliability (coefficient alpha of .91 and .70, respectively) and correlate highly with the overall SUS (r = .985 and .784, respectively). They also correlate significantly with each other (r = .664), but at a low enough level to be used as separate scales. A sensitivity analysis using data from 19 tests showed a significant Test by Scale interaction, further supporting the differential utility of the new scales. Practitioners can continue to use the standard SUS as is, but can also benefit from these new scales to extract additional information from their SUS data. The data also support the use of "awkward" rather than "cumbersome" in Item 8.