Born 1 December 1867 at Civitavecchia, where his father was in general practice, he studied at the United Hospitals at Rome and graduated there in 1892. He served as clinical assistant to Francesco Durante, Hon FRCS. He was surgeon at San Giacomo Hospital 1903-05 and at the Umberto Policlinic 1905-23. Alessandri was a supreme teacher, particularly interested in this aspect of his work. He was director of the Institute of Surgical Pathology at Rome, 1902-19, and professor of clinical surgery in the university, 1919-38, in succession to Durante. In the war of 1914-18 he was director of the second army surgical service, and won the silver medal for valour; he operated under fire at the battle of Gorizia. In 1927 he was nominated a senator of the kingdom of Italy. Towards the end of his life Alessandri was paralysed, but he retained his mental faculties and continued to study current surgical literature and to write on surgery. He died in Rome of cerebral thrombosis on 8 August 1948, aged 80. Alessandri was an all-round surgeon. He practised surgery of the nervous system, of epilepsy, of spinal-cord tumours, and of pulsating skeletal tumours. He was among the first to perform coledocho-duodenostomy, and early advocated radical intervention for gastro-duodenal ulcer; he also studied post-operative peptic ulcer. He made successful ligation of hepatic and splenic arteries, and operated for hepatic cirrhosis. He experimented in transplanting embryonic tissues, and with osseous transplants. He operated for chronic osteomyelitic abscess, and studied the diseases of the parathyroid. As first director of the Forlanini Institute for Thoracic Surgery, he was a pioneer in Italy of the operations of apicolysis, thoracoplasty, and lobectomy. He was president of the Italian Surgical and Anaesthetic Societies, of the Academy of Medicine at Rome, and of the International Society of Urology. He was editor of the surgical section of *Policlinico* and joint editor of *Annali di chirurgia*. After retiring he worked on a *Treatise of surgery* but did not complete it. His pupils compiled a *Manual of surgery* in five volumes in his honour. Shortly before his death he wrote a chapter on "Operations on the spinal column" for the *Operative medicine*, edited in his name by Luigi Torraca.