Quasar clustering and cosmology: observational status

The importance of quasars as probes to underline large-scale structures of the Universe is emphasized. Recent work on quasar clustering detection is discussed. The methods used to detect and characterize quasar clustering are analysed and compared within each other. The possible evolution with redshift of quasar clustering at small-scale separation is discussed and compared to other types of clustering at low and high redshift. Figures are given of typical survey sizes needed to significantly improve the present observational status