Low-temperature hydrothermal reactions of metakaolinite have been investigated, with and without additions of silica, by use of the bases LiOH, NaOH, RbOH, and CsOH and also the mixtures NaOH + LiOH, NaOH + KOH, KOH + LiOH, and NaOH + Me₄NOH. Over certain temperature and composition ranges reproducible crystallisation fields have been obtained for all the above bases and pairs of bases. Two hydrated non-zeolites were formed (nepheline hydrate I and a near-hectorite), and also a group of anhydrous phases. However under the conditions employed zeolitisation reactions were dominant, which are largely but not fully paralleled by similar reactions with aqueous alkaline aluminosilicate gels. A number of the products have been characterised by X-ray, d.t.a., t.g.a., and sorption studies, and in other ways. The most frequently occurring zeolite phases were those related to phillipsite, gismondite, gmelinite, chabazite, faujasite, Linde A type, sodalite and cancrinite hydrates, and two lithium zeolites and a sodium tetramethylammonium zeolite without natural counterparts.