This article examines variation between null and overt subject pronouns in ASL. In ASL, information about the subject is sometimes provided through morphology. Certain verbs allow changes in form (i.e., in their use of space) that indicate the person and/or number of the subject. In the case of plain verbs (Padden 1988), however, the verb form itself includes no information about the subject. Although we might expect plain verbs to require separate manual subjects, they also show variable subject presence. In this study, based on spontaneous narratives produced by signers ranging from 16 to 84 years of age, we use multivariate analysis to examine the behavior of subjects of plain verbs. All possible sites of pronominal subjects occurring with plain verbs were coded for a number of factors, including person and number, switch reference, sentence type, age, and gender. We also coded for whether the token occurred within constructed action or dialogue or within utterances marked by obvious English influence. Overall, results indicate that ASL subject pronoun presence with plain verbs is systematic and constrained by a range of factors that exhibit remarkable similarity to constraints found in studies of spoken languages. Results for age, however, need to be interpreted in light of the social history of the U.S. Deaf community.