Abstract The aim of this pictorial review is to demonstrate the diverse presentations of the medial insertion of pectoralis major on mammography. A collection of cases demonstrating the variations in appearance of this muscle insertion are presented. The factors contributing to the appearances of this artifact, the differential diagnoses and useful further investigations are discussed. Familiarity with the different presentations of this muscle insertion will facilitate recognition and prevent unnecessary investigations. Cawson, J. N. and Papadopoulos, T. (2002). Clinical Radiology 57, 442–448.