On July 23, the IRS released Notice 2004-50, which is the most comprehensive health savings account (HSA) guidance issued to date. The Notice resolves many issues in a manner that is generally favorable for employers, insurers, and trustees. However, the IRS position with respect to certain issues may result in increased cost and complexity of HSA administration. In Part I below, we provide a background of HSAs and previous guidance provided by the IRS and Department of Labor; in Part II, we summarize the major issues that the IRS resolved, both favorably and unfavorably, in this guidance; and in Part III, we offer some additional observations on the new rules.