ThIS volume contaInS a selectIOn of InvIted revIew papers presented at a Royal SocIety DIscussIOn meetIng on ThIn FIlm DIamond held In London on 15 and 16 July 1992 The topIC of low pressure synthesIs has attracted world wIde Interest and become IncreasIngly active In recent years due to the pOSSIble use of dIamond films In commerCIal apphcatlOns Until recently commercIal dIamond synthesIs was almost entIrely by the hIgh pressure hIgh temperature technIque In whIch dIamond IS precIpItated as an eqUlhbnum phase from a carbon-contaInIng hqUld metal catalyst In thIS way crystals may be formed up to 10mm or so In sIze The metastable low pressure techmques cannot compete In cost but can be used to fabrIcate large area wafers or predetermIned shapes not pOSSIble by other means Most of the low pressure techmques stem from the work of Eversole whICh was first reported In 1962 He exposed a hot dIamond substrate alternately to a hydrocarbon gas, whIch deposIted a mIxture of dIamond and graphIte, and then to hydrogen, whICh preferen- tIally etched away the graphite In later developments th~se two stages have been combIned to form a contInUOUS process and dIffer only In the way the etchant IS generated In thIS volume an hIstorIcal overvIew of these low pressure growth techmques and a deSCrIptIOn of dIamond and crystal morphology IS gIVen by John Angus and hIS co-authors In theIr paper on the chemICal vapour depOSItIon of dIamond James Butler and RIchard WoodIn