Empirical analysis of IRA accumulation and withdrawal patterns is limited because information about IRA balances and flows is not available for a sample of taxpayers. This paper combines survey data on IRA balances with individual tax return data on IRA flows to study IRA accumulation and withdrawal patterns across cohorts. The analysis shows that IRA rules such as penalties for early withdrawals and minimum distribution requirements have predictable effects on IRA flows. The estimated propensities to contribute to IRAs, rollover from pensions, and withdrawal from IRAs are used to project IRA flows and balances in the near to medium term.