We are presenting new results on K+/- and pi(+/-) production in minimum bia
s lead-lead collisions at 158 A GeV/c. The measurements were performed at z
ero degree production angle and for a wide rapidity range. The analysis met
hod used the full particle identification capabilities (time of flight, Cer
enkov counters and hadronic calorimeter) of the spectrometer. We show K/pi
and pi(-)/pi(+) ratios as a function of rapidity, as well as invariant part
icle production cross sections. As a particularity we observe near projecti
le rapidity an enhancement in the number of pi(-) with respect to pi(+).