Prolonged grief disorder (PGD) is a severe psychiatric condition that occurs in about 10% of people who experience a recent loss. PGD does not just go away with time and is associated with considerable functional impairment, physical and mental health problems, lost productivity, lack of interest in previously enjoyed activities, suicide, and depression. Because the majority of people with PGD are elderly and less capable of pursuing outside care, making readily available treatments for PGD is very important. Current treatments for PGD include psychotherapy and antidepressant medications, but there is very little solid research on the effectiveness of these treatments. Previous studies have shown that Internet-based mental health treatments are an effective and cost-efficient way to provide self-help to people who otherwise would not seek care. Using strategies from the psychotherapy known as cognitive behavioral therapy (CBT), this study will evaluate the effectiveness of an Internet-based self-help program in treating people who are at risk for developing prolonged grief disorder following a recent loss.