OBJECTIVE To test the hypotheses that ED patients' desires for medical information and for autonomy in decision making are inversely related to increasing acuity of illness, increasing age, and lower level of formal education. METHODS The authors conducted a prospective study of ED patients who presented for care during seven nonconsecutive 24-hour periods. Of 804 patients approached, 665 completed a questionnaire that was administered by a trained research assistant. Patients rated their desire for medical information, and for participation in medical decision making, on two 10-cm visual analog scales. Patient acuity level was determined in routine fashion by trained triage nurses, who were unaware of the nature of this study. RESULTS Desire for information was uniformly high, and did not vary statistically between triage groups (p = 0.41). The most acutely ill patients (level I) were more likely to be excluded by the research interviewer (p < 0.001). Of included level I patients, desire to participate was not decreased (p < 0.01). Higher level of formal education (p = 0.036) and younger age (p < 0.001) were associated with greater desire for autonomy in decision making. CONCLUSIONS Among ED patients able to participate, higher acuity of illness was not associated with a decreased desire for medical information. Many very acutely ill patients preferred autonomy in medical decision making. Older patients and those with less formal education expressed a lesser desire for decision-making autonomy.