A safe, simple, rapid and very sensitive technique is described for the quantitative estimation of phospholipid phosphorus. In comparison with other procedures, our method is shown to be particularly advantageous for very diluted phospholipid solutions,The main feature of the method was the acid digestion of large volumes in Kjeldahl flasks. After neutralization, the inorganic phosphate was determined spectrophotometrically.Using soybean lecithins, both the precision and accuracy of the method were elaborated. The coefficient of variation amounted to at most 1 . 5 % and the sensitivity was reduced to 500 nM of phospholipids.