Data from the Longitudinal Survey of Income and Program Participation were used to examine the dynamics of health insurance among persons 55 to 64 years of age. Persons in this age range are especially vulnerable to incurring high health care costs. Between the summer of 1983 and early 1986, 21% of persons 55 to 64 years of age experienced some time without health insurance. Approximately one fifth were continuously uninsured (4%) while the rest spent only part of the time without coverage, typically 4 months or less. Women were particularly vulnerable to periods without insurance, accounting for approximately twice as many of them as did men. Unlike younger cohorts, the coverage lost among the near elderly tended not to be employer coverage. Instead, most uninsured spells were ones in which individually purchased coverage was lost. Most spell beginnings were unrelated to changes in household employment, yet most spells ended when employment within the household increased. Some currently proposed reforms to expand health insurance, such as an all-employer mandate, a "pay-or-play" mandate, and extending Medicaid to persons in poverty, are less effective in reaching this medically high-risk population than in reaching younger persons who are uninsured.