Abstract The semi-inclusive cross section for a + b → c + ( n- t-1) charged + anythings neutral is investigated in Feynman's gas (liquid) model, where only the two-particle inclusive correlation function is taken into account. It is shown that this model leads to the semi-inclusive scaling recently proposed by Koba, Nielsen and Olesen (for those multiplicities where the model leads to positive definite cross section). The general case where many-particle correlations are included, is briefly discussed. It is conjuctured that for multiplicities n ⪢ 〈 n〉 the semi-inclusive distribution function factorizes in momentum and “relative multiplicity” n/〈 n〉. The experiment K + + p → K o + n charged + anything neutrals is compared with Feynman's gas model. Qualitative agreement is found.