  At present, the ground-based astronomy of very high energy (VHE) (E>100 GeV)
gamma-rays experiences the challenging transition phase caused by the
substantial upgrading of its observational instrumentation. Recently the HEGRA
collaboration has evidently demonstrated the power of arrays of imaging
atmospheric Cherenkov telescopes and initiated a number of complementary
projects, such as H.E.S.S., CANGAROO IV, VERITAS. The common philosophy of
those projects is based on the stereoscopic observations of air showers with a
number of imaging telescopes simultaneously. Such observations allow to reduce
substantially the effective energy threshold of detected gamma-ray showers; to
improve the angular and energy resolution for individual gamma-rays; to gain in
suppression of the cosmic ray background. In my talk I have summarized the
general advantages and achieved sensitivity of the stereoscopic observations
using the HEGRA data taken with an array of 5 imaging telescopes having the
energy threshold of 500 GeV. These results completed with the relevant
simulations may be extrapolated on a firm ground towards the future H.E.S.S.
(phase I) array of four 12 m imaging telescopes with the estimated energy
threshold below 100 GeV. Here I discuss in short the anticipated performance of
such an array.
