This paper uses data from the 1999 and 2002 rounds of National Survey of Americas' Families to examine variation and trends in the duration of uninsurance. The results show that 49 million people were uninsured at some time during the 2001-2002 period, with over half (26 million) being uninsured for 12 months or longer. Rates of short-term uninsurance for various subgroups were often similar, while rates of long-term uninsurance varied widely and accounted for large differences in overall uninsurance rates. Although a slightly smaller share of the population was uninsured for 12 months or more in 2002 than in 1999, the overall change in the rate of uninsurance was small.