The bis(aroyloxymethyl) esters of benzylphosphonate 8(XPh, ArPh, 2-MeC6H4 or 2,4,6-Me3C6H2) and methoxycarbonylmethylphosphonate 8(XMeO2C, ArPh, 2-MeC6H4 or 2,4,6-Me3C6H2) have been prepared by reaction of 2 equiv. of the appropriate aroyloxymethyl iodide with the disilver salt of either benzylphosphonate or methoxycarbonylmethylphosphonate. The cyclohexylammonium salts of the mono(aroyloxymethyl) esters of benzylphosphonate 12(XPh, ArPh, 2-MeC6H4 or 2,4,6-Me3C6H2, M+C6H11NH3+) were prepared by reaction of silver benzyl benzylphosphonate with the appropriate aroyloxymethyl iodide, with subsequent hydrogenolysis to remove the P-O-benzyl group. The bis(aroyloxymethyl) esters 8(XPh or MeO2C, ArPh, 2-MeC6H4 or 2,4,6-Me3C6H2) and the mono(aroyloxymethyl) salts 12(XPh, ArPh, 2MeC6H4 or 2,4,6-Me3C6H2, M+C6H11NH3+) were stable towards chemical hydrolysis at 37 °C at physiological pH. In the presence of porcine liver carboxyesterase, the bis(aroyloxymethyl) esters of benzylphosphonate 8(XPh, ArPh or 2-MeC6H4) degraded to the mono(aroyloxymethyl) esters 12(XPh, ArPh or 2-MeC6H4,), which showed slow hydrolysis to benzylphosphonate. For the bis(aroyloxymethyl) esters of methoxycarbonylmethylphosphonate 8(XMeO2C, ArPh or 2MeC6H4) there was competition between the esterase-catalysed hydrolyses of the aroyloxymethyl and methoxycarbonyl groups. For the triester 8(XMeO2C, Ar2,4,6-Me3C6H2) cleavage of the methoxycarbonyl group was observed and hydrolysis of the sterically hindered 2,4,6-trimethylbenzoyl group (Ar2,4,6-Me3C6H2) was not detected for any compound.