The infrared-active localized modes of oscillation of defect-oxygen complexes in electron-irradiated and neutron-irradiated silicon containing oxygen are reported. Behavior with heat treatment and relative intensities show the existence of a large number of complexes besides the Si-B1 center responsible for the line at 835 cm-1. Neutron-irradiated silicon exhibits satellite lines close to the 835 cm-1 line when such specimens are annealed above 473°K. Isochronal-annealing studies indicate that the satellite centers are not associated with the Si-B1 center. Multiple-vacancy centers in association with dispersed oxygen may account for the satellites.