Born on 25 June 1890 he was one of the sons of Gustav Julius Hellström, an electrical engineer, and Carolina Cecilia Osterberg. They lived at Katrineholm and he commenced his education in Katrineholm Primary School, later proceeding to Norrköping Grammar School. He began his preclinical medical studies at Uppsala University and for his clinical training went to the Karolinska Hospital in Stockholm, qualifying with the primary degree at Karolinska Institute in Stockholm on 24 November 1917. His first clinical appointment was at Vänersborg Hospital working under Olof Lundblad. Later he was a registrar at the Sahlgrenoka Hospital in Gothenburg, taking his MD examination by thesis at the Karolinska Institute in Stockholm. After this he became resident surgical officer at the Maria Hospital in Stockholm becoming a consultant and working under Einar Key. When Einer Key died Hellström was appointed to succeed him as Professor of Surgery in 1939 where he remained until 1958. He was a general surgeon with a definite preference for urology. He operated upon King Gustav V and was honoured as a Knight of the Order of the North Star. The Swedish Society of Surgeons awarded him their Acrel medal. He founded the department of urology at the Karolinska Hospital and he was President of the International Society of Urology at the meeting in Stockholm in 1958. For many years editor of *Acta chirurgica scandinavica*, he contributed over two hundred papers, particularly on the etiology of urinary calculi and on carcinoma of the prostate. A smallish dynamic personality he usually dominated any medical meeting he attended. He married first Maria Clareus, who died in 1946, and secondly in 1948 Sonia Katarina Staaf, who survived him. There were no children by the second marriage but a daughter by the first. He died in Stockholm on 1 September 1965 aged seventy four.