  We consider $K^-$ nucleon elastic and inelastic scattering in isospin
symmetric nuclear matter. It is found that the proper description of the
$\Lambda(1405)$ resonance structure in nuclear matter requires a
self-consistent approach. Then the $\Lambda (1405) $ resonance mass remains
basically unchanged, however, the resonance acquires an increased decay width
as nuclear matter is compressed. The elastic and inelastic scattering
amplitudes show important medium modifications close to the kaon nucleon
threshold. We also construct the $K^-$-nuclear optical potential appropriate
for $K^-$ atoms. Our microscopic approach predicts a strong attractive
non-local interaction strength.
