Shirley Ardell Mason passed away on February 26, 1998, at the age of 75. She achieved a notable career in psychology for her work on the topic of multiple personality disorder, working extensively with the condition. Mason wrote five books on the disorder, and also worked professionally with patients. She often appeared in the media to talk about her research and quickly became one of the leading figures in public awareness of multiple personality disorder. Her life’s work will continue to be studied and remembered.