We analyze what functions as a YES response and a NO response for different yes/no questions. This problem is surprisingly complex: respondents do not always produce overt yes or no lexical items in sponse to a yes/no question. In addition, when spondents don't include a clear yes or no word, they may mean to communicate a clear YES or NO ing, or something else. We find that the classification of yes/no questions described in (Carletta et al., 1995) for the Edinburgh map task corpus correlates well with whether a response will be a bare yes or no, a yes or no plus additional speech, or just speech out an overt yes or no. Correlation with responses described simply as as "direct" or "indirect" is less good. We also find that, under the three-way rization, the strength of a question's expectation for a YES response predicts the form of the response.