Born at Brussels on 21 May 1877, he graduated at the Université libre de Bruxelles in 1901. He served as Chef-de-Service to Antoine Depage at Wellebroeck and also at the Institut Médico-Chirurgical at Brussels where he became Agrégé for surgery in 1905. He published many papers on cancer research and various aspects of abdominal surgery. Over and above his active surgical career he did much to promote internationalism in surgery and postgraduate education. He founded in 1921 the successful weekly journal *Bruxelles-Médical* and edited it for thirty-five years, until his death. Under the influence of his master Depage he organised the Société internationale de Chirurgie, became its secretary-general in 1914, and succeeded in preserving its records during the first world war. In the years between the wars its biennial Congresses achieved a great success, and Mayer was responsible for organising these and for editing their *Proceedings*. He was elected President in 1947, and subsequently President of Honour, but continued to work actively at the Society's routine business, and edited its quarterly *Journal* and *Bulletin*. He promoted the successful Journées-Médicaux of postgraduate refresher courses at Brussels, which were afterwards imitated in France and other countries, and was president of the standing committee of these Journées. He was an honorary member of the Académie Royale de Médecine of Belgium. Mayer lived at 72 Rue de la Loi, Brussels, with his office at 141 Rue Belliard. He died in Brussels on 27 August 1955 aged 78, survived by his son and collaborator Dr Charles Mayer.