Among multiple slippage effects potentially generated in voluntary land retirement programs, this study attempts to identify one unique source of slippage. Specifically, I examine slippage caused by within-a-farm land conversion from uncultivated land to cropland. With the U.S. Agricultural Census farm-level longitudinal data on land use and enrollment in the Conservation Reserve Program (CRP), I find that an average partial-farm CRP participant converts 25% of noncropland to cropping activities as a consequence of CRP enrollment. Also, an estimated slippage rate varies across farm types and regions. In particular, farms with relatively inelastic crop acreage supply lead to more slippage. Knowledge about the mechanisms through which slippage occurs should help policymakers devise programs with features designed to avoid or mitigate slippage incentives.