Building on research that identifies and addresses issues of women's underrepresentation in computing, this article describes promising practices in undergraduate research experiences that promote women's long-term interest in computer science and engineering. Specifically, this article explores whether and how REU programs include programmatic elements designed to promote gender equity and identifies specific mechanisms that are seen as effective in supporting women in REU programs and in encouraging them to persist in computer science and engineering fields. The findings are drawn from a comprehensive study that includes a national survey of REU programs, follow-up interviews with REU program directors from across the country, and an in-depth evaluation of one REU program over four years. (Contains 1 table and 1 footnote.)