1 Introduction

In the last decade the study of the evolution of the QSO luminosity function and of the clustering properties of QSOs has been based on statistical analysis of even larger QSO catalogues. For redshifts lower than 2.2 the color techniques provide good selection methods. Now days the QSO luminosity function evolution at z<2.2 is well established (e.g. La Franca & Cristiani 1997; Goldschmidt & Miller 1998). This kind of studies are mainly based on the most statistically significant QSO samples such us the Durham/AAT QSO sample (Boyle et al. 1990) at faint magnitudes (B<20.9), and the Bright QSO Survey (Schmidt & Green 1983), the Large Bright QSO Survey (Hewett et al. 1995), the Edinburgh UVX QSO survey (Goldschmidt et al. 1992; Miller et al. in preparation), the Homogeneous Bright QSO Survey (HBQS, Cristiani et al. 1995) at bright magnitudes (B<18.5). In total these samples collect about a thousand of QSOs with z<2.2. But these samples are still not ideally suited to study the QSO clustering and its evolution (see Andreani & Cristiani 1992). The best QSO samples for clustering analysis should have the highest possible surface densities and cover a contiguous areas, such as the planned QSO 2dF redshift survey (Croom et al. 1998).

In order to improve the signal-to-noise ratio in the estimate of the clustering of QSOs, we have built a new sample of 429 QSOs down to $B_{\rm J}=20.5$ over a contiguous area of 24.6 deg². This sample has allowed the measure of a difference on the QSO clustering evolution in comparison with that found for galaxies (La Franca et al. 1998).

The survey is located in the south Galactic pole (SGP) region, where some of the Durham/AAT sample areas are included (Boyle et al. 1990), and part of the high-redshift QSO survey of Warren et al. (1991b) was carried out. The region has been also studied by Campusano (1991). The central area of 1.7 deg² in our region has been covered by the ESO Imaging Survey in the B, V and I band (EIS, da Costa 1998; Nonino et al. 1999; Prandoni et al. 1999; Zaggia et al. 1999). The acquisition of the corresponding U data is planned for 1999. Further deep multicolor imaging over an area of about half a sq deg is planned with the WFI at the ESO 2.2 m telescope. Moreover about 10 deg² of the southern area of the region is included in the 2dF QSO redshift survey (Croom et al. 1998).