The purpose of this paper is to encourage the use of field weighting over field interpolation in achieving grid-area parity in principal component analysis of geophysical data. While field weighting has been shown to achieve exact parity in unrotated analysis, we show that it is highly effective in rotated analysis, too, by comparing the three leading modes of 200-mbar geopotential height variability in the 1958--1998 NCEP reanalysis winters obtained from both methods. ¿ 1999 American Geophysical Union