Phosphatidylcholines (PC) are a class of phospholipids that incorporate choline as a headgroup. They are a major component of biological membranes and can be easily obtained from a variety of readily available sources, such as egg yolk or soybeans, from which they are mechanically or chemically extracted using hexane. They are also a member of the lecithin group of yellow-brownish fatty substances occurring in animal and plant tissues. Dipalmitoyl phosphatidylcholine (a.k.a. lecithin) is a major component of pulmonary surfactant and is often used in the L/S ratio to calculate fetal lung maturity. While phosphatidylcholines are found in all plant and animal cells, they are absent in the membranes of most bacteria,[1] including Escherichia coli.[2] Purified phosphatidylcholine is produced commercially.

The body makes a brain chemical called acetylcholine from phosphatidylcholine. Acetylcholine is important for memory and other bodily functions. Since phosphatidylcholine might increase acetylcholine, there is interest in using it for improving memory and for conditions such as Alzheimer's disease.

Some researchers think phosphatidylcholine acts like a detergent and breaks down fat.

A certain form of phosphatidylcholine (polyunsaturated phosphatidylcholine) might provide protection against liver fibrosis and liver damage caused by drinking alcohol, although the exact mechanisms are not completely understood.