Intolerance of ambiguity is the perception of ambiguous situations as a threat. Medical students with differing levels of intolerance of ambiguity may select medical specialties based upon the amount of ambiguity existing in the practice of each specialty. A cross-sectional survey at one state university administered Budner's Intolerance of Ambiguity Scale to all entering first-year medical students for four consecutive years (N = 609) to investigate patterns of intolerance of ambiguity in relationship with demographic variables and initial medical specialty preference. The medical students in this study were more intolerant of ambiguity than those first studied by Budner in 1962. Students entering in 1985 were slightly more intolerant of ambiguity than students in 1988. Students age 23 and older were less intolerant of ambiguity than students 18-22 years old. Men and students with natural/physical science undergraduate majors were more intolerant of ambiguity than their counterparts. However, medical specialty preference was not related to intolerance of ambiguity. Intolerance of ambiguity may be a personality trait or a learned characteristic, and needs further investigation.