CONTENTS[br] 1. Introduction 381[br] 2. A Brief Reveiw of the Experimental Data at Accelerator Energies . . . 382[br] 3. The Statistical-Hydrodynamic Approach 386[br] 4. Fragmentation Models 388[br] 5. The Multiperipheral Model and the Reggeon Scheme 389[br] 6. Quark Models 393[br] 7. Comparison with the Experimental Data 394[br] 8. Interactions with Nuclei 397[br] 9. The Space-Time Picture 399[br] 10. Very High Energies 401[br] 11. Conclusions 402[br] Cited Literature 402