This paper, based on the rapporteur talk given at the XXIV International Cosmic-Ray Conference (Roma, 28 August - 8 September 1995), concerns the sessions HE1, HE2, HE6. Multihadron production in cosmic rays, models, emulsion chamber measurements, simulation of electromagnetic and hadronic cascades, new particles and processes are summarized in the frame of the special phenomenology adapted to the collisions of ultrahigh-energy particles in the atmosphere.