Angiotensinase activity was characterized in human red blood cells (RBC), RBC ghosts and rabbit adrenal cells. Using paper chromatography it was found that each of these preparations possess enzymes capable of converting angiotensin II to its heptapeptide derivative, [des-Asp1] angiotensin II (angiotensin III). Further characterization of these enzymes by the use of a chromogenic assay indicates that although intact RBC do not split sarcosine-.beta.-naphthylamide, RBC ghosts do. Intact rabbit adrenal cells from the zona glomerulosa show activity against sarcostine-.beta.-naphthylamide. Non-specific angiotensinases are present on the inside of the RBC membrane and the outside of the adrenal cell membrane.