Secondary negative and positive charge emission coefficients for bombardment of a gas‐covered Cu surface by H+, H0, and H−have been measured for projectile energies of ∼25–2500 eV. The secondary negative charge yield for H0impact was found to be 1.15±0.08 times that for H+impact. For H−impact, the secondary negative charge yield decreased less rapidly with projectile energy than that of H+and H0impact, being about an order of magnitude larger at the lowest energies investigated. The secondary positive charge yields were found to be independent of the projectile charge state and were about an order of magnitude smaller than the negative charge yields. The measurement techniques are described, and the results are compared with the data of other investigators.