Variation in the parts of ASL signs (i.e., phonological variation) has been explained largely by reference to the influence of the preceding and the following segments. This article examines three linguistic variables in ASL: the sign deaf; the location of a class of signs represented by the verb know; and signs produced with a 1 handshape. For all three of these variables, a multivariate analysis of more than nine thousand tokens extracted from videotaped conversations among 207 signers in seven sites across the United States shows that the grammatical function of a sign, rather than the features of the preceding or following signs, is the most important influence on a signer's choice among the variants. In addition to providing evidence for the role of this previously unexamined influence on variation in ASL, the results of this study highlight the importance of basing claims about the likely causes of variation on empirical studies of broadly representative samples of data collected in the language community. (Contains 4 figures, 7 tables and 11 notes.)