  Extensive air showers are generated through interactions of high-energy
cosmic rays impinging the Earth's atmosphere. A new method is described to
infer the attenuation of hadrons in air showers. The numbers of electrons and
muons, registered with the scintillator array of the KASCADE experiment are
used to estimate the energy of the shower inducing primary particle. A large
hadron calorimeter is used to measure the hadronic energy reaching observation
level. The ratio of energy reaching ground level to the energy of the primary
particle is used to derive an attenuation length of hadrons in air showers. In
the energy range from $10^6$ GeV to $3\cdot10^7$ GeV the attenuation length
obtained increases from 170 \gcm2 to 210 \gcm2. The experimental results are
compared to predictions of simulations based on contemporary high energy
interaction models.
