Abstract 2-Aminoethylphosphonic acid (AEPA) and its N-substituted compounds were prepared by one step reaction using 2-chloroethylphosphonic acid with ammonia and amines (H2NMe, HNMeMe, HNEtEt, H2NPr-n, H2NCH2ph, H2NCH2CH2NH2 and H2N(C=NH)NH2 in a dilute alkaline solution below 20 °C with simple work-up and easy purification. The reaction was accelerated by catalytic amount of potassium iodide. The