Depression is a common psychiatric disorder affecting approximately 17 million Americans each year and resulting in a significant economic burden, estimated at $43-$53 billion in 1990. The cost burden of depression extends beyond the direct cost of treatment, to include the costs of lost productivity, both while at work and days absent from work, as well as lost earnings due to increased mortality and the impacts experienced by a patient's caregivers. This range of costs is discussed, in the context of the prevalence and impacts of depression and detailing the cost components of depression. We highlight that existing estimates of the cost of depression are underestimates and we conclude with areas for future research.