Coherence effects and perturbative QCD tests with the OPAL detector at LEP

I report on results and methods from a set of analyses performed within the OPAL collaboration at CERN. The full available data sample collected at and near the Z/sup 0/ resonance is used. Results concern colour-field interference and coherence phenomena, quark and gluon jet properties, identified particles in quark and gluon jets, measurements of the QCD colour factors and relevant tests of recently improved perturbative QCD calculations. The challenge is that QCD is a quantum field theory that requires all orders in perturbation theory and non-perturbative analysis to confront data at available energies. Thus, precise measurements can be thought as explorations of quantum field theory itself. Nonetheless, these tests and measurements have important practical applications, in the calculation of backgrounds to new physics and, for hadron collider particularly, in predictions for new particle cross-sections. (184 refs).