We review the current status of QSO clustering measurements , particular with respect to their relevance in understanding AGN physics .
Measurements based on the 2dF QSO Redshift Survey ( 2QZ ) find a scale length for QSO clustering of s _ { 0 } = 5.76 ^ { +0.17 } _ { -0.27 } h ^ { -1 } Mpc at a redshift \bar { z } \simeq 1.5 , very similar to low redshift galaxies .
There is no evidence of evolution in the clustering of QSOs from z \sim 0.5 to z \sim 2.2 .
This lack of evolution and low clustering amplitude suggests a short life time for AGN activity of the order \sim 10 ^ { 6 } -10 ^ { 7 } years .
Large surveys such at the 2QZ and SDSS also allow the the study of QSO environments in 3D for the first time ( at least at low redshift ) , early results from this work seem to show no difference between the environments of QSOs and normal galaxies .
Future studies e.g .
measuring clustering as a function of black hole mass , and deep QSO surveys should provide further insight into the formation and evolution of AGN .