A PROCESS FOR THE PRODUCTION OF MONO- AND DIHALOGENEATED GEM-DIPHOSPHONATE ESTERS (C3-C8) AND MONOAND DIHALOGENTAED PHOSPHONOACETATE ESTERS (C5-C7) IS DISCLOSED. DIBROMINATED AND DIIODATED GEM-DIPHOSPHONATE ESTERS CONTAINING ALKYL GROUPS HAVING THREE TO EIGHT CARBON ATOMS, DICHLORINATED GEM-DIPHOSPHONATE ESTERS CONTAINING ALKYL GROUPS HAVING FROM 7 TO 8 CARBON ATOMS, AND MONOHALOGENATED GEM-DIPHOSPHONATE ESTERS CONTAINING ALKYL GROUPS HAVING FROM 7 TO 8 CARBON ATOMS, AS NOVEL COMPOUNDS, ARE ALSO DISCLOSED. THE GEM-DIPHOSPHONATE ESTERS ARE USEFUL AS INTERMEDIATES IN THE SYNTHESIS OF DETERGENT BUILDERS AND AS EXTREME PRESSURE AND ANTI-WEAR ADDITIVIES IN LUBRICANT CMPOSITIONS. THE PHOSPHONOACETATE ESTERS ARE USEFUL AS EXTREME PRESSURE AND ANTI-WEAR ADDITIVIES IN LUBRICANT CMPOSITIONS.