Spectroscopic observations of the edge-on spiral galaxy NGC 891 confirm the existence of ionized gas well above its central plane. Hα can be traced to z > 30" corresponding to z > 1.4 kpc. Alternative situations-an incorrect aspect ratio, a warp in the plane, or scattering from extraplanar dust-are considered and rejected. Eleven spectrograms positioned parallel and perpendicular to the plane show that this gas is in cylindrical rotation to at least z = 0.7 kpc, to within the accuracy of measurement, 25 km s^-1^. Corotation is most readily understood if this high-z gas originates within the disk. The structure and physical state of this extraplanar ionized gas are discussed.
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Keppel et al. (1991) studied this question.