  We construct a complete list of O(q^4) terms directly within Heavy Baryon
Chiral Perturbation Theory (HBChPT) in the absence of external fields and
assuming isospin symmetry. In addition to a phase rule recently developed
(NPA646, 343, '99), a variety of algebraic identities and reparameterization
invariance, are used to ensure linear independence of the terms and their low
energy coupling constants. We first construct O(q^4) terms terms for off-shell
nucleons, and then perform the on-shell reduction, again within HBChPT. We
discuss an application of the O(q^4) terms to the evaluation of the O(q^4)
operator insertions in the "contact graph" of pion double charge exchange.
