The nation's private defined benefit (DB) pension system, a key contributor to the financial security of millions of Americans, is in long-term decline. Since 1980, the number of participants in insured single employer DB plans has dropped from 27% in 1980, to 15% in 2002. Hybrid DB plans like cash balance (CB) plans may be a means to revitalize this declining system. This report: reviews current research about the implications of CB conversions for employee benefits; describes the prevalence & type of transition provisions used to protect workers' benefits in past CB conversions; & estimates the effects of CB conversions on the benefits of individual participants under a hypothetical conversion to a typical CB plan from a typical traditional DB plan.