Gibson, said to be the world's tallest dog, died Friday from cancer near Sacramento. He was 7 years old and 7 feet tall when stretching out on his hind legs.
Gibson, who lived in Grass Valley and was named tallest - at just under 43 inches from his shoulder to the ground - by the Guinness Book of World Records, was diagnosed in April with osteosarcoma, a form of canine bone cancer, which led to the amputation of his front right leg.
The surgery was performed to prevent the cancer from spreading, and early tests showed positive results.
After the surgery, the harlequin Great Dane received follow up chemotherapy treatments as a precaution.
Last week, Sandy Hall, Gibson's owner, learned that the cancer had spread to Gibson's lungs and spine, at which point Gibson's doctor stated that there was no other medical treatment that would save Gibson.
"Last week Gibson began having trouble using his back legs," said Dr. Peter Walsh, Gibson's veterinarian, in a prepared statement. "X-rays showed that the cancer had spread to his spine and his lungs. Ms. Hall made the very difficult decision based on her concern and love for Gibson to have him humanely euthanized. Gibson died peacefully in the loving arms of Ms. Hall."
Hall will continue her work with Three Paws for the Cause, her initiative to raise awareness of canine cancer.
A new Web site, www.remembergibson.com, has been established to promote Three Paws for the Cause and honor Gibson's memory. The site features a memorial page where fans can pay tribute to him and express their condolences.