The invention relates to cationic water-soluble polyelectrolytes, especially terpolymers, which are obtained by polymerising monomers of (meth)acrylamide, a quaternised (meth)acrylamide derivative, a (meth)acrylic acid derivative and/or hydrolysis-stable cationic monomers. The composition of the polyelectrolytes is characterised by a toxicity index formula Fi=(QTP-2QME)/10.ltoreq.1 wherein QTP represents the total cationic charge of the polymer and QME represents the charge part of the ester type monomer. The invention also relates to the production and use of said polyelectrolytes and water-in-water polymer dispersions which contain said polyelectrolytes.