William Brown settled at Maitland early in 1842. He announced the opening of his surgery in the Hunter River Gazette stating he was a Licentiate of the Faculty of Physicians and Surgeons in Glasgow. He hoped to practice as a Surgeon and Accoucheur in East Maitland and had previously owned a successful practice of considerable duration in Scotland. His surgery was to be situated at Mr. Ree's in East Maitland and to commence on Monday 7th February.
He brought with him from Scotland a considerable stock of medicines and offered to supply those who employed him at a rate much below that usually charged in the colony.
Death of children was not uncommon in the 1830's; many did not survive infancy. In 1844 William Brown performed a post mortem on a seven week old baby who had died at Mulberry Creek. He stated that in his opinion death was caused by disease on the external surface which led to irritation occasioning fever. The disease on the skin had been caused by want of sufficient nourishment and improper food and the baby had been much emaciated with multiple abscesses on her head and hands. He considered gruel improper food for so young a child; he considered arrow root, sago, and milk to be the most proper food for such a child. The baby's mother had lost her milk due to a breast abscess and it was thought this would be very prejudicial to a child so young. Scarcely any artificial food could be found to supply its place and even with the best of care children in such circumstances may die. 
William Brown worked hard to save the life of the son of Charles Wilson in 1848. The four year old had ventured too near a horse feeding in his father's yard. The horse kicked him in the side of the head, fracturing his skull. Dr. Brown attended at once and found part of the brain protruding from the wound. Unable to restore it, he removed the protruding portion. The little boy was partially sensible throughout this ordeal and later died.
William Brown died at East Maitland on 3rd December 1859 aged 39 years