Summary Acetone powders prepared from sheep SME fragments were extracted with acetic acid and subjected to gel filtration on Sephadex G-25. An LH-releasing zone was eluted from the column just before the appearance of the pressor zone. The LH-releasing zones from 3 such columns were pooled, applied to a CMC column, and eluted by application of gradients of ammonium acetate of increasing ionic strength and pH. A pressor free LH-releasing zone was eluted from the CMC just prior to emergence of vasopressin. This highly purified LH-RF was active at a dose of 3 μg of peptide. Preliminary desalting was required in order for the LH-RF to be retained on the CMC column. Various steps and stages of desalting have been discussed.