BY HENRY TAUBER AND EDWARD L. PETIT RECEIVED NOVEMBER 8, 1952 The preparation of 50 phosphonic and phosphinic acids has been described recently from our laborat0ry. l These compounds were examined for their anti-plasma cholinesterase activity. Several of the compounds were found to be quite active. A few of the acids were esterified. Most of the esters were much more active against human plasma cholinesterase than the ...