Although English is generally considered to be an alphabetically written language some of it is in fact written ideographically. For example, numbers can be written in both forms of script (e.g. 1 or ONE). The present experiments demonstrate that these script forms yield differences in a comprehension task. When normal subjects are asked to judge which of two simultaneously displayed numbers is numerically the larger, irrelevant variations in the physical size of the numbers influence response time when the numbers are printed ideographically, but not when they are printed alphabetically. These results, coupled with the neuropsychological observation that patients who are alexic but not agraphic can name numbers when they are written ideographically but are greatly impaired when the numbers are written alphabetically, suggests that these different script forms engage different processing mechanisms.