  A severe problem of the research in star-formation is that the masses of
young stars are almost always estimated only from evolutionary tracks. Since
the tracks published by different groups differ, it is often only possible to
give a rough estimate of the masses of young stars. It is thus crucial to test
and calibrate the tracks. Up to now, only a few tests of the tracks could be
carried out. However, with the VLTI it is now possible to set constrains on the
tracks by determining the masses of many young binary stars precisely. In order
to use the VLTI efficiently, a first step is to find suitable targets, which is
the purpose of this work. Given the distance of nearby star-forming regions,
suitable VLTI targets are binaries with orbital periods between at least 50
days, and few years. Although a number of surveys for detecting spectroscopic
binaries have been carried out, most of the binaries found so far have periods
which are too short. We thus surveyed the Chamaeleon, Corona Australis, Lupus,
Sco-Cen, rho Ophiuci star-forming regions in order to search for spectroscopic
binaries with periods longer than 50 days, which are suitable for the VLTI
observations. As a result of the 8 years campaign we discovered 8 binaries with
orbital periods longer than 50 days. Amongst the newly discovered long period
binaries is CS Cha, which is one of the few classical T Tauri stars with a
circumbinary disk. The survey is limited to objects with masses higher than 0.1
to 0.2 Modot for periods between 1 and 8 years. We find that the frequency of
binaries with orbital periods < 3000 days is of 20+/-5 percent. The frequency
of long and short period pre-main sequence spectroscopic binaries is about the
same as for stars in the solar neighbourhood. In total 14 young binaries are
now known which are suitable for mass determination with the VLTI.
