Although the title of this paper is “Reversions in Theory and Practice,” the greater part of these remarks will deal with the practical side, as it is essentially a practical subject. Those who deal with reversions will at once agree with the necessity for practical experience, a little of which is worth a great deal of theory. Mr Collins concludes his lectures on reversions with the advice, “Do not flummox yourself with formulae till you can't see the wood for the trees,” but I think that that admirable warning would really form a better preface. A glance through the writings on our subject will reveal at once a lack of complicated formulae. An absolute reversion is valued simply by the appropriate “A” factor and for a contingent reversion, there is merely deducted from the “A,” the cost of providing against whatever contingencies may be involved. Before one gets to that point, however, other considerations are necessary.