  Heavy baryon chiral perturbation theory including spin 3/2 delta resonances
as effective degrees of freedom is reviewed. The theory admits a systematic
expansion in the small scale $\epsilon$, where $\epsilon$ collectively denotes
soft momenta, the pion mass or the delta-nucleon mass difference.
Renormalization is discussed in some detail on the example of the scalar sector
of one-nucleon processes, and a reformulation of the principle of resonance
saturation for counterterms of the HBChPT lagrangian is sketched. As an
application, the polarizabilities of the nucleon are discussed at order
$\epsilon^3$.
