This invention relates to the modification of elastomers by reaction with unsaturated silanes, to the modified elastomers produced and to articles produced by shaping and curing modified elastomer compositions. In a process according to the present, the silane has the formula: R″—CH═CH—C(O)X—Y—SiRaR′(3-a) (I) or R″—C≡C—C(O)X—Y—SiRaR′(3-a) (II) in which R represents a hydrolysable group; R′ represents a hydrocarbyl group having 1 to 6 carbon atoms; a has a value in the range 1 to 3 inclusive; Y represents a divalent organic spacer linkage comprising at least one carbon atom separating the linkage —C(O)X— from the Si atom, X is S or O; and R″ represents hydrogen or a group having an electron withdrawing effect with respect to the —CH═CH— or —C═C— bond; and the silane is reacted with the diene elastomer in the absence of any free radical initiator. This is advantageous because free radical initiators such as peroxides tend to degrade diene elastomers. In addition, safe handling and mixing of peroxides can be difficult for rubber compounders. The grafted diene elastomer produced has improved adhesion to substrates, for example reinforcing cords and fabrics used as reinforcement in rubber articles such as tyres.