Direct spectroscopic evidence of high-density regions in the Orion Neb
ula, N(e) almost-equal-to 10(5)-10(7) cm-3, is obtained from the forbi
dden optical and near-IR [Fe II] emission lines, using new atomic data
. Calculations for level populations and line ratios are carried out u
sing 16, 35, and 142 level collisional-radiative models for Fe II. Est
imates of Fe+ abundances derived from the near-infrared and the optica
l line intensities are consistent with a high density of 10(6) cm-3 in
the [Fe II] emitting regions. Important consequences for abundance de
terminations in the nebula are pointed out.