  The modern status of basic low energy QCD parameters is reviewed. It is
demonstrated, that the recent data allows one to determine the light quark mass
ratios with an accuracy 10-15%. The general analysis of vacuum condensates in
QCD is presented, including those induced by external fields. The QCD coupling
constant alpha_s is found from the tau-lepton hadronic decay rate. V-A spectral
functions of tau-decay are used for construction of the V-A polarization
operator Pi_{V-A}(s) in the complex s-plane. The operator product expansion
(OPE) is used up to dimension D=10 and the sum rules along the rays in the
complex s-plane are constructed. The best values of quark condensate and
alpha_s<0|qq|0>^2 are found. The value of quark condensate is confirmed by
considering the sum rules for baryon masses. Gluon condensate is found in four
ways: by considering of V+A polarization operator based on the tau-decay data,
by studying the sum rules for polarization operators momenta in charmonia in
vector, pseudoscalar and axial channels. All of these determinations are in
agreement and result in <(alpha_s/pi)G^2 > =0.005 \pm 0.004 GeV^4. Valence
quark distributions in proton are calculated in QCD using the OPE in proton
current virtuality. The quark distributions agree with those found from the
deep inelastic scattering data. The same value of gluon condensate is favoured.
