The BH masses are correlated against a variety of nuclear and host-galaxy properties. Nuclear properties such as line width and line ratios show a very high degree of correlation with BH mass. The excellent correlation with line width supports the view that the emission-line gas is in virial equilibrium with either the BH or bulge potential. The very good emission-line ratio correlations may indicate a change in ionizing continuum shape with BH mass in the sense that more massive BHs generate harder spectra.

Apart from the inclination-corrected rotational velocity, no excellent correlations are found between BH mass and host-galaxy properties.

Significant differences are found between the distributions of BH masses in early (S0/a, Sa), middle (Sab-Sbc) and later (Sc) type spiral galaxies in the sense that early-type galaxies have preferentially larger central BHs. The line-width distributions show a marked difference among the sub-samples in the sense that earlier-type galaxies have larger line widths. There are also clear differences in line ratios between sub-samples likely related to the level of ionization in the gas.

Finally, a K_s-band Simien & de Vaucouleurs diagram shows excellent agreement with the original B-band relation.