Two experiments addressed these questions: Do deaf signers agree on the location of sign boundaries in American Sign Language? and Where in time are the boundaries located? First 35 ASL sign sequences were edited out of sentence contexts and slowed to 1/10 normal speed. Six deaf observers judged the beginning and ending of a test sign in each videotaped sequence. The observers agreed on the location of sign boundaries and relied on changes in facial expression, hand configuration, or manual movement differences as visual cues for the boundaries. Second, hearing subjects judged the same videotape sequences. Comparing results indicated that the deaf subjects were using linguistic knowledge of ASL and not a general perceptual strategy when making judgments of the location of sign boundaries.