Abstract: The invention concerns a water-in-oil polymer emulsion containing in an organic and continuous phase practically non-miscible in water, finely comminuted water soluble polymers or capable of being swollen in water, a water-in-oil emulsifying agent and optionally wetting agents. The invention also concerns a method for preparing said emulsion. More particularly, it concerns a method for invert emulsion in the presence of one or several initiators belonging a specific family of azacarboxylic acid esters.