We use QCD sum rules to obtain the weak parity-violating pion-nucleon
coupling constant f(pi NN). We find that f(pi NN) approximate to 2 x 1
0(-8), about an order of magnitude smaller than the ''best estimates''
based on quark models. This result follows from the cancellation betw
een perturbative and nonperturbative QCD processes not found in quark
models, but explicit in the QCD sum rule method. Our result is consist
ent with the experimental upper limit found from F-18 parity-violating
measurements.