William Dearden studied at Owens College, Manchester, qualifying LSA and MRCS in 1885; he took the DPH in 1889. He was in general practice at Blackley and Crumpsall, Manchester, and was a certifying factory surgeon. Dearden served as secretary and president of the Association of Certifying Factory Surgeons. He was later medical officer of health for the Manchester Port Authority. He was an acknowledged expert in diseases affecting cotton workers, and delivered the Milroy lectures to the Royal College of Surgeons in 1927 on this subject. He was active in the British Medical Association and was president of its Section of Occupational Diseases in 1929. He was also chairman of the medical board at Stretford Memorial Hospital. Dearden published several articles on industrial medical services.