1.A study was made of the reaction of (C6H5)3P=CHCOOCH3with nitro aldehydes, and the methyl esters were prepared of o-, m-, and p-nitrocinnamic acids, 2,4,6-trinitrocinnamic acid, and 5-o-nitrophenyl-2,4-pentadienoic acid.2.On the assumption that the preparation of methyl o-nitrocinnamate can be taken as typical it was shown that the reaction proceeds stereospecifically with formation of the trans form.