Water-soluble complexes of lanthanum(III), cerium(III), neodymium(III) and erbium(III) with N-Phosphonomethylglycine (glyphosate, NPMG) of the general formulae: LaC3H5NO5P .H2O, CeC3H5NO5P .H2O, NdC3H5NO5P .1,5H(2)O, ErC3H5NO5P . 2H(2)O were synthesized. Their solubility in water was determined. Thermal, diffractometric and IR spectrophotometric analyses were carried out. It was found that the lanthanide ions are bonded to N-phosphonomethylglycine through the oxygen atoms of the carboxylic and phosphonate groups and the nitrogen atom of the amine group. The final products of thermal decomposition at 900 degreesC were determined.