[en] Some CP odd observables are proposed to test CP invariance in the t t-bar system proceeded at p p-bar and pp colliders. As CP violation can appear both in the production and in the decays of the top quarks, it is important to separate the effects from each other by using different observables. These will be discussed and some comments on using the observables for pp colliders are also made. Numerical results for these observables are given together with their sensitivity to the new CP violating interactions. 17 refs, 1 fig