Abstract: Silicone compositions which, when exposed to atmospheric moisture at room temperature cure to form a flame retardant elastomer comprising (a) an organopolysiloxane having terminal hydroxyl groups, (b) a cross-linking agent having an average of at least three functional groups linked to a silicon atom per molecule, in which the functional groups are selected from the group consisting of hydrocarbonoxy groups, amine groups, aminoxy groups, oxime groups and mixtures thereof, (c) a condensation catalyst, (d) platinum metal or compound thereof, (e) carbon black, (f) alumina hydrate and optionally (g) a filler.The resultant flame retardant silicon elastomers are useful as insulation for electrical equipment, as encapsulants and as sealants where flame retardancy is necessary.