Authorities disagree as to whether and how the mental capacity required for competence to stand trial should change as the charges against a defendant become more serious. Intuition and practice in other areas of law and psychiatry suggest that the mental capacity required should increase in these circumstances. The reasons relate to our belief that serious mistakes are more to be avoided and to a principle of "proportionality," according to which the threshold level of capacity required is derived, in part, from the consequences of a person's being found competent. The article compares two approaches to "proportionality." The conclusions have implications for the wording of examiners' conclusions and for the criteria by which patients are regarded as "restored to competence."