  We calculate the threshold T-matrices of kaon-nucleon and antikaon-nucleon
scattering to one loop order in SU(3) heavy baryon chiral perturbation theory.
To that order the complex-valued isospin-1 $\bar KN$ threshold T-matrix can be
successfully predicted from the isospin-0 and 1 $KN$ threshold T-matrices. As
expected perturbation theory fails to explain the isospin-0 $\bar KN$ threshold
T-matrix which is completely dominated by the nearby subthreshold
$\Lambda^*(1405)$-resonance. Cancelations of large terms of second and third
chiral order are observed as they seem to be typical for SU(3) baryon chiral
perturbation theory calculations. We also give the kaon and eta loop
corrections to the $\pi N$ scattering lengths and we investigate $\pi\Lambda$
scattering to one-loop order. The second order s-wave low-energy constants are
all of natural size and do not exceed 1 GeV$^{-1}$ in magnitude.
