Rat platelet lysate contained appreciable phospholipase A, activity. In agreement with literature data this enzymatic activity eluted in the void volume of a Sephadex G-100 column. When the void volume peak was chromatographed over a Matrex gel blue A column, part of the phospholipase A, activity ran through, whereas the remainder was bound to the gel. The latter activity could be eluted with buffers containing a high salt concentration. In contrast, phospholipase A, activity solubilized from rat platelet lysates by treatment with high salt eluted from Sephadex G-100 columns with an apparent molecular weight of lo-15 kDa.