A new procedure has been developed for the synthesis of 1-aminophosphonic acids. Diethyl phosphonates are converted to hydroxyiminophosphonates when treated with hydroxylamine hydrochloride. Reduction of hydroxyiminophosphonates with NaBH4 in MeOH in the presence of MoO3 or NiCl2 and hydrolysis of 1- aminophosphonates gave 1-aminophosphonic acids in good yield.