AbstractAlpha‐melanocyte‐stimulating hormone (α‐MSH), one of several peptide hormones originating in the intermediate lobe of the pituitary as proopiomelanocortin, was discovered in bovine pituitary intraglandular colloid by using radioimmunoassay. The quantity of α‐MSH varied from 5 to 368 μg/mg protein in the three pools. The importance of this finding is discussed in light of the possibility that the colloid is a transport medium for α‐MSH and other intermediate