ABSTRACTThe present observational and theoretical status of multiple-supernova remnants is briefly reviewed, and evolutionary models of the remnants around OB associations are presented. The remnants are followed for up to almost 30 Myr in various galactic environments (Gaussian or composite disks combined with cold or hot halos). It is found that the presence of a hot halo profoundly modifies the evolution of the remnants, promoting the evaporation of their shells and leading to noneruptive merging of the ejecta with the halo gas. The results also suggest an explanation for the observed deficiency of evolved multiple-supernova remnants.