Building up assets and avoiding excessive debt can help families insure against unforeseen disruptions, achieve economic independence, and reach the middle class. Asset building, however, can be difficult for many low- and moderate-income families, who must overcome many economic obstacles and work off high liabilities to accumulate adequate net worth. This brief examines the levels and assets and debts, saving behaviors, and variations in these data across representative samples of American families in order to identify populations least able to accumulate assets, and examine factors that are linked to asset-building in financially vulnerable households.