Tenure fraction has become recognized as an important factor to be taken into account in the administration of institutions of higher education, but there is danger that pursuit of lower fractions per se may lead to actions that unnecessarily weaken the institution or its educational programs. With the aid of an extremely simple mathematical model of a faculty of constant size, five common methods of affecting tenure fractions are found to rank in decreasing order of effectiveness approximately as follows: reduction of the fraction of nontenured faculty granted tenure, delay in awarding tenure, increase in the average age of hiring nontenured faculty, reduction of the mandatory requirement age, reduction of the fraction of direct appointment to tenure. The institutional flexibility gained by a reduction in tenure fraction may be accompanied by substantial advantages such as enhanced competence of the faculty, but offsetting short-term or long-term costs may be incurred in terms of money, faculty morale, and ability to attract the desired kind of new faculty members, unless the methods chosen are carefully matched to the goals of the institution. Before the general policies for the institution can be applied to its component parts, attention must be given to such special situations as small size, student enrollments, or a fast-changing body of knowledge. (Author)