  We report the variation of the spectral energy distribution (SED) of blazars
as a function of source activity, based on available, simultaneous
multi-wavelength (MWL) observations of BL Lac objects. We use a fully
automatized \c{hi}2 minimization procedure, instead of the commonly used
eye-ball fit, to model the data sets with a one-zone Synchrotron-Self-Compton
(SSC) model. The obtained SSC parameters are then analyzed as a function of
source luminosity, and the correlation between parameters is shown.
Possibilities of improving the present observational and modeling status of BL
Lac objects are also discussed.
