Apathy is common in Alzheimer's disease (AD) but may be confused with depression due to overlap in symptoms queried in depression assessments. Depression and dysphoria appear to occur less frequently in AD but are better researched. This study examined the relative frequency of these syndromes and their relation to disease characteristics in 131 research participants with probable or possible AD. Apathy was more prevalent than dysphoria or major depression and was more strongly associated with global disease severity, cognitive impairment, and functional deficits. Accurate differential diagnosis of apathy and depression is key to appropriate family education and effective treatment.