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The statistical distributions of the number of simultaneously emitted secondary electrons (SE’s) from a thin carbon foil induced by the frozen-charged H 0 and H+ projectiles of 2.5–3.5 MeV have been measured by using the coincidence technique with the foil-transmitted particles. The measurement was carried out at the forward and backward directions of the incident beam separately. For frozen-charged H 0, the average SE yields per projectile at the forward direction, γ F, and at the backward direction, γ B, are significantly smaller than the corresponding ones for H+ due to the screening effect of its bound electron. In addition to the suppression of low-energy electron production for H 0, the preferential forward emission of high-energy electrons makes the proton-hydrogen difference in the ratio of γ B to the stopping power more striking. Although the probability of simultaneous n electron emission per unit projectile …