  This paper presents the sixth part to the Very Long Baseline Array (VLBA)
Calibrator Survey. It contains the positions and maps of 264 sources of which
169 were not previously observed with very long baseline interferometry (VLBI).
This survey, based on two 24 hour VLBA observing sessions, was focused on 1)
improving positions of 95 sources from previous VLBA Calibrator surveys that
were observed either with very large a priori position errors or were observed
not long enough to get reliable positions and 2) observing remaining new
flat-spectrum sources with predicted correlated flux density in the range
100-200 mJy that were not observed in previous surveys. Source positions were
derived from astrometric analysis of group delays determined at the 2.3 and 8.6
GHz frequency bands using the Calc/Solve software package. The VCS6 catalogue
of source positions, plots of correlated flux density versus projected baseline
length, contour plots and fits files of naturally weighted CLEAN images, as
well as calibrated visibility function files are available on the Web at
http://vlbi.gsfc.nasa.gov/vcs6
