1 Introduction

Starting in August 1990 a European Network of Laboratories "Visual Double Stars'' was founded for combining the efforts of scientists in six European countries with the goal to obtain accurate ground-based photometric and astrometric data on visual double and multiple stars as a complement to the HIPPARCOS space observations (Oblak et al. 1992). In 1992 a key programme was introduced at the European Southern Observatory (ESO) aiming at obtaining the photometry and the astrometry of visual double stars in the southern hemisphere: photoelectric and CCD photometry would be carried out. A full scientific and technical description of this large scale project can be found in Oblak et al. (1999, Paper I). Cuypers & Seggewiss (1999, Paper II) report on the results of the two campaigns that immediately preceded the key programme observations. In this paper (Paper III) we report on the final results of five campaigns of the ESO key programme. Preliminary results of the combined data sets on the one hand and external comparisons with HIPPARCOS data on the other hand have already been presented on several occasions (Lampens et al. 1997; Oblak et al. 1997).