  We discuss the relationship between a standard Shakura & Sunyaev (1973)
accretion disk model and the Big Blue Bump (BBB) observed in Type 1 AGN, and
propose a new method to estimate black hole masses. We apply this method to a
sample of 23 radio-loud narrow-line Seyfert 1 (RL-NLS1) galaxies, using data
from WISE (Wide-field Infrared Survey Explorer), SDSS (Sloan Digital Sky
Survey) and GALEX. Our black hole mass estimates are at least a factor $\sim$6
above previous results based on single epoch virial methods, while the
Eddington ratios are correspondingly lower. Hence, the black hole masses of
RL-NLS1 galaxies are typically above $10^8 M_{\sun}$, in agreement with the
typical black hole mass of blazars.
