  Heavy baryon chiral perturbation theory is briefly reviewed, paying
particular attention to the role of the spin 3/2 delta resonances. The concept
of resonance saturation for the baryonic sector is critically discussed.
Starting from a relativistic formulation of the pion-nucleon-delta system, the
heavy baryon chiral lagrangian including spin 3/2 resonances is constructed by
means of a 1/m-expansion. The effective theory obtained admits a systematic
expansion in terms of soft momenta, the pion mass $M_\pi$ and the delta-nucleon
mass difference $\Delta$.
