Patients' reactions to uncertainty were investigated using a hypothetical clinical situation that involved lower extremity pain and stiffness. Subjects' uncertainty avoidance was observed under varying types and sources of uncertainty, using a short questionnaire distributed to 306 outpatients and spouses at two hospital locations. It was found that 21.0 percent of the subjects would avoid an ambiguous treatment with the same success probability level at which they previously accepted a nonambiguous treatment; 33.7 percent of the subjects preferred to defer the treatment decision to the physician altogether. Confidence and the context of the decision were related to ambiguity avoidance, and decision avoidance was related to age. The implications of these findings for medical decision making are discussed in relation to the nonunitary nature of partial uncertainty.