A comparison has been made of the vulcanization of NR in the latex form and in the dry form. In latex form, NR was found to vulcanize at a much faster rate than in the dry form. The faster rate of reaction in latex prevulcanizatIon is attributed to the presence of the aqueous phase which acts as a medium for the dissolution of ZDBC and sulphur, and provides a suitable environment for the two vulcanizing ingredients to react to form the active sulphurating agent. A comparison has also been made of the prevulcanization behaviour of NR latex and synthetic cis-polyisoprene latex. It has been suggested that the indigenous vulcanization accelerators and activators present in NR latex act as additional vulcanizing accelerators and therefore increase the rate of prevulcanization.