This article uses conversation analysis to develop a typology of questions that physicians use to solicit patients' problems and then tests question-format effects on patients' subsequent problem presentations. Data are videotapes of 302 primary-, acute-, and outpatient-care visits involving 77 physicians in 41 urban and rural clinics, as well as pre- and post-visit questionnaires. The most frequent question formats were general inquiries (62%; e.g., "What can I do for you today?") and requests for confirmation (27%; e.g., "I understand you're having some sinus problems today?"). Compared to confirmatory questions, general inquiries were associated with significantly longer problem presentations ( p<.0001) that included more discrete symptoms ( p<.0001). Physicians were more likely to use confirmatory questions in the urban setting ( p=.003).