After preliminary studies of CH4 in solid argon and hydrogen, the infrared absorption spectra of matrix-isolated SiH4 and SiD4 in solid argon, hydrogen, and deuterium at 2-4 K were measured. The two infrared-active nu (4) (bending) and nu (3) (asymmetric stretching) regions were observed. The absence of bands due to absorption from the J = 1 excited rotational state in the ground vibrational level indicates that (1) the nuclear spin conversion is relatively rapid and (2) the silane molecules are not rotating or are highly hindered rotationally in these matrices at 2 and 4 K. The SiH3 radical was observed in solid hydrogen; it was produced by photolysis of the silane/hydrogen matrix with radiation from a hydrogen discharge.