We discuss the unidirectional current screen as an asymptotic strip boundary condition (ASBC) for analysis of field problems containing metal strip grids, and we introduce a related asymptotic corrugation boundary condition (ACBC) for analysis of corrugated surfaces. The boundary conditions ale asymptotic in the sense that the exact boundary conditions approach the asymptotic ones when the strip and corrugation periods approach zero. (C) 1997 John Wiley & Sons, Inc.