Toland located his office near the waterfront at Montgomery and Merchant Streets and soon became the city's foremost surgeon. He frequently reported on surgical operations in the Pacific Medical and Surgical Journal, revealing a practice that included bone surgery, vesico-vaginal fistula repair, iridectomy for glaucoma, thyroidectomy, and repair of aneurysms. In 1855, he was appointed surgeon to the State Marine Hospital, the predecessor to the City and County Hospital of San Francisco. In 1864, he founded the Toland Medical College, intending that this medical school should "spring into usefulness and become an ornament to the city and an honor to the state." This school was transferred as an unconditional gift to the University of California in 1873, and became the Medical Department of this young institution.
In addition to his activities as surgeon and Professor of Surgery, Toland's interest in pharmacy and his experience in the mother lode added to his thriving medical practice the delivery of packaged medicines to the miners. Toland used the Wells Fargo messengers to carry his advice and medicines up to the mining country. His favorite remedies, labeled "anti-scroft" (iodide of potash) and "anti-syph" (mercury with a dash of lobelia), were used to treat the common problems of tuberculosis and syphilis. Although many writers stress the rowdy, entrepreneurial nature of Toland's mail order business, his work as a serious surgeon and medical educator represents his important contributions to California medicine. He died suddenly of stroke at age 74 while still "hale and systematic" and active in his Montgomery Street practice.