Research suggests that few children who are reliant on manual sign for expressive communication progress beyond a basic level of sign combinations. However, they may be capable of expressing complex meanings by changing the form of their signs. This study investigated whether children with intellectual disabilities could be taught productive use of modified signs. Eight children participated in a matrix-based intervention program to teach sign modifications that were contrastive, generalized, and consistent. Results indicated that modified signs could be systematically taught. There was also evidence to suggest that the children were beginning to use modified signs productively. However, it is suggested that their patterns of use were more characteristic of a gestural than a linguistic system.