We present a model that relates the width of the broad emission lines of ac
tive galactic nuclei (AGNs) to the Keplerian velocity of an accretion disk
at a critical distance from the central black hole. This critical distance
falls in a region bounded on the inward side by the transition radius betwe
en the radiation pressure- and the gas pressure-dominated region of the acc
retion disk and on the outward side by the maximum radius below which a sta
bilizing, radially accreting and vertically outflowing corona exists. We sh
ow that in the framework of this picture, the observed range of H beta FWHM
s from broad-line to narrow-line type 1 AGNs is well reproduced as a functi
on of the accretion rate. This interval of velocities is the only permitted
range and goes from similar to 20,000 km s(-1) for sub-Eddington accretion
rates to similar to 1000 km s(-1) fur Eddington accretion rates.