We studied the interaction between hydrogen and point defects generated by electron irradiation of Si by means of optical absorption measurement. Specimens were prepared from n-type Si crystals. Those specimens were doped with hydrogen by annealing in a hydrogen atmosphere at 1200 • C followed by quenching and were subsequently irradiated with 3 MV electrons at room temperature. We observed their optical absorption spectra at about 6 K with a resolution of 0.25 cm −1 . Many optical absorption peaks were observed in electron-irradiated specimens. Most of those peaks disappeared at around 300 • C due to isochronal annealing. On the other hand, new optical absorption lines appeared at 2223 cm −1 and 2166 cm −1 after annealing at high temperature, namely above 150 • C. The former is known to be due to a complex of one self-interstitial atom and 4 hydrogen atoms. We propose that the 2166 cm −1 peak is due to a complex of one self-interstitial atom and three hydrogen atoms. These results clearly show that complexes of self-interstitials exist after electron-irradiation of Si and they dissociate above 150 • C.