In this chapter, we discuss early warning signs, which are signs and symptoms that often occur before an episode of psychosis. These signs and symptoms, though mild, may occur before the first episode of psychosis and also before later episodes. That is, some mild signs and symptoms may occur during the prodromal phase of the illness, before psychotic symptoms first develop. These same signs and symptoms often serve as warning signs before another episode of illness, or a relapse of psychosis, occurs. So, it is important to be familiar with early warning signs and what to do if they begin to develop. Many people who have had a first episode of psychosis will go on to have one or more relapses of their illness. A relapse happens when symptoms appear again. Some relapses may happen with little or no warning over a short period of time, such as a few days. However, most relapses develop slowly over longer periods, like a few weeks. A relapse may or may not require hospitalization, but it definitely calls for immediate attention, evaluation, and treatment. After a stay in the hospital or after outpatient stabilization, some people feel better quickly. Others take weeks, or even months, to function as well as they had before the relapse. One way of avoiding a relapse is to stay in treatment and attend all follow-up appointments (see Chapter 8 on Follow-up and Sticking with Treatment). Also, it is very important to become aware of one’s specific early warning signs, which are changes in thoughts, feelings, and behaviors that happen a few days or weeks before an episode (reappearance of symptoms). By carefully watching for these signs, patients, their families, and their mental health professionals can work together to help lessen the severity of any episode that may occur. Relapse prevention is the goal of preventing a relapse altogether, by sticking to treatment and watching for early warning signs. The first step in determining one’s specific early warning signs is to think back to the changes that occurred in the prodromal period of the illness, or the time just before the first episode of psychosis. While there are common early warning signs, they will show up slightly differently in each person. Early warning signs in one person may be clear and easy to detect, while in another person they may be trickier to figure out. Early warning signs are signals that symptoms are beginning again and that another episode of psychosis may happen.