Process for the preparation of phosphatidylserine of formula wherein R.sup.1 and R.sup.2 independently represent a saturated, mono-unsaturated or polyunsaturated acyl C.sub.10-C.sub.30, X.dbd.OH or OM where M=alkaline or alkaline earth metal, ammonium, alkylammonium (including the inner salt) including the transphosphatidylation reaction between phosphatidylcholine of the general formula wherein R.sup.1 and R.sup.2 and X have the above specified meanings, R.sup.3.dbd.CH.sub.2--CH.sub.2--NH.sub.2 o CH.sub.2--CH.sub.2--N.sup.+(CH.sub.3).sub.3 and Serine in D, L or racemic form catalysed by the phospholipase D enzyme (PLD), characterised in that said reaction is carried out in a hydroalcoholic medium containing an aliphatic alcohol and in the presence of bivalent metal oxide.