  We present spectroscopic observations of ionized gas in the disk-halo regions
of five edge-on galaxies, covering a wavelength range from [OII] 3727A to [SII]
6716.4A. The inclusion of the [OII] emission provides additional constraints on
the properties of the diffuse ionized gas (DIG), in particular, the origin of
the observed spatial variations in the line intensity ratios. We have derived
electron temperatures, ionization fractions and abundances along the slit. Our
data include both slit positions parallel and perpendicular to the galactic
disks. This allowed us to examine variations in the line intensity ratios with
height above the midplane as well as distance from the galactic centers. The
observed increase in the [OII]/Halpha line ratio towards the halo seems to
require an increase in electron temperature caused by a non-ionizing heating
mechanism. We conclude that gradients in the electron temperature can play a
significant role in the observed variations in the optical emission line ratios
from extraplanar DIG.
