  The production of K^+ mesons in pA (A = D, C, Cu, Ag, Au) collisions has been
investigated at the COoler SYnchrotron COSY-J\"ulich for beam energies T_p =
1.0 - 2.3 GeV. Double differential inclusive pC cross sections at forward
angles theta < 12 degrees as well as the target-mass dependence of the K^+
momentum spectra have been measured with the ANKE spectrometer. Far below the
free NN threshold at T_{NN}=1.58 GeV the spectra reveal a high degree of
collectivity in the target nucleus. From the target-mass dependence of the
cross sections at higher energies, the repulsive in-medium potential of K^+
mesons can be deduced. Using pN cross-section parameterisations from literature
and our measured pD data we derive a cross-section ratio of sigma(pn -> K^+ X)
/ sigma(pp -> K^+ X) ~ (3-4).
