Cross-sections of high-energy hadron-nucleus reactions σ h (A) are investigated using ther optical model. A closed formula is drived for σ h (A); itsA-dependence agrees with the rms radius of the Fermi distribution of nuclear matter. The properties of the radius parameter and the absorption mean free pathλ h are investigated using Serpukhov data forp, πα,K ± , and $$\bar p$$ . It is foundλ p =1.44 ± 0.23 fm ∼-1/m π andλ π =2.14 ± 0.21 fm forp and π-reactions, respectively; withλ π /λ p ≃3/2 as expected from quark-counting. The approach extended to heavyion (HI) reactions leads to a formula of Bradt-Peters type, with an overlapping parameter decreasing withA. Analyses of HI data of LBL and ISR with this formula are presented.