CompHEP, as a partonic event generator, and PYTHIA, as a generator of final states of detectable objects, are interfaced. Thus, integrated package is created for simulation of (almost) arbitrary collision processes at the detector level. Exact (multiparticle) matrix elements, convolution with structure functions together with decay, hadronization and (optionally) parton shower procedures are basic stages in the calculations. The problem of automatic resummation of large logarithms (higher order corrections) is discussed. Experience of the creation the PEVLIB library of event generators for LHC processes is discussed.