  Multiplicities in semi-inclusive deep-inelastic scattering are presented for
each charge state of \pi^\pm and K^\pm mesons. The data were collected by the
HERMES experiment at the HERA storage ring using 27.6 GeV electron and positron
beams incident on a hydrogen or deuterium gas target. The results are presented
as a function of the kinematic quantities x_B, Q^2, z, and P_h\perp. They
represent a unique data set for identified hadrons that will significantly
enhance our understanding of the fragmentation of quarks into final-state
hadrons in deep-inelastic scattering.
