Résumé : The values of the topological cross-sections for {Mathematical expression} interactions at 32 GeV/c are derived from a sample of ∼74 000 events observed in the Mirabelle bubble chamber. The parameters of the charged-particle multiplicity distribution are compared with similar data at other energies and with those obtained for pp interactions. The difference between the {Mathematical expression} and pp topological cross-sections provides parameters for {Mathematical expression} annihilation. © 1982 Società Italiana di Fisica.