1. Introduction

2. The XBS sample of type 1 AGN

3. Black-hole mass
3.1. Line width measurements
3.2. Monochromatic luminosities
3.3. Computing the BH masses
3.4. Uncertainties on BH Masses
3.5. Comparison of the black hole mass estimates

4. Eddington ratio and M

5. The effect of radiation pressure

6. Summary and conclusions