  A method is proposed for measuring the size of the broad emission line region
(BLR) in quasars using broadband photometric data. A feasibility study, based
on numerical simulations, points to the advantages and pitfalls associated with
this approach. The method is applied to a subset of the Palomar-Green quasar
sample for which independent BLR size measurements are available. An agreement
is found between the results of the photometric method and the spectroscopic
reverberation mapping technique. Implications for the measurement of BLR sizes
and black hole masses for numerous quasars in the era of large surveys are
discussed.
