This document specifies two methods for the determination of the surface tension of polymer dispersions and rubber latices (natural and synthetic). — Method A is the ring method (Du Noüy ring method). — Method B is the plate method (Wilhelmy plate method). Method A is suitable valid for polymer dispersions and rubber latices with a viscosity less than 200 mPa·s. Method B is not suitable for polymer dispersions and rubber latices containing cationic surfactants. Methods A and B are also suitable for prevulcanized latices and compounded material. In case of dispute, the preferred method is method A (the ring method).