In a study of pd annihilation reactions between 1.09 and 1.43 GeV/c, it is found that the four- and six-prong samples with a visible slow proton exhibit features substantially different from those expected based on a simple impulse approximation. A phenomenological model, developed in the framework of Galuber's model, provides an excellent description of the data. In as much as 26.6% of the three- and four-prong and 21.7% of the five- and six-prong samples, pions from one of the annihilation reactions interact with the spectator nucleon via either elastic or charge-exchange scattering. This process is called the final-state interaction. For the initial-state interaction in which the incident antiproton undergoes elastic scattering prior to annihilation, the process accounts for 7.5% (9.1%) of the three- and four- (five- and six-) prong events. © 1981 The American Physical Society.