  We present the results of a long-term variability survey of the old open
cluster NGC 6791. The BVI observations, collected over a time span of 6 years,
were analyzed using the ISIS image subtraction package. The main target of our
observations were two cataclysmic variables B7 and B8. We have identified
possible cycle lenghts of about 25 and 18 days for B7 and B8, respectively. We
tentatively classify B7 as a VY Scl type nova-like variable or a Z Cam type
dwarf nova. B8 is most likely an SS Cygni type dwarf nova. We have also
extracted the light curves of 42 other previously reported variable stars and
discovered seven new ones. The new variables show long-period or non-periodic
variability. The long baseline of our observations has also allowed us to
derive more precise periods for the variables, especially for the short period
eclipsing binaries.
