Phospholipase D (phosphatidylcholine phosphohydrolase EC 3.1.4.4) is an enzyme which plays an important role in the phospholipid metabolism. This enzyme is widespread in both the plant and animal kingdoms. It has been reported to play an important role in signal transduction cascades in a variety of mammalian cells. In the case of plants, PLD is known to be involved in several cellular processes, but its actual role has not in fact yet been clearly established. In this review, recent advances in plant PLD research are summarized. In the first part, we describe the methods used to purify PLD from various plant species and discuss its catalytic properties. The second part deals with various aspects of PLD enzymology, based on studies using phosphatidylcholine substrate integrated into the detergent micelles. In the last part the structural data available are reviewed and comparisons are made between various plant PLD sequences. The possible physiological role of PLD in plants is discussed.