  We analyse a subsample of the galaxy groups obtained by Merch\'an &
Zandivarez (2005) from the SDSS DR3 to study the fundamental plane and the mass
to light ratio of galaxy groups. We find a fundamental plane given by $L_R
\propto R^{1.3} \sigma^{0.7}$. We do not find differences when different
dynamical sates or redshift ranges are analysed. We find that the mass to light
ratio increases with group mass as $M/L_R \propto M^{0.36}$.

Astrophysics