A simple way of synthesising 2-(arylamino)ethyl phosphonic esters and acids via the aza-Michael addition of amines to diethyl vinylphoshonate ‘on water’ was developed. Various 2-(arylamino)ethyl phosphonates were initially produced through the condensation of primary and secondary amines with diethyl vinylphosphonate, focussing on those bearing one aromatic moiety, giving generally good to high yields