This paper reports regularities of stress placement at the phrasal level in American Sign Language (ASL) and identifies a category of signs (final pronouns) that appear to be exceptions. The group of exceptional pronouns predominantly comprises experiencer subject arguments, a category that does not traditionally participate in the verb agreement system of ASL, creating a morphological gap. Evidence is presented that some of these pronouns may be in the process of grammaticalizing to verbal suffixes which may serve to fill the morphological gap.