The interaction of O-2 with Pd(110) has been studied by TDS and XPS at T = 400 K and at pressures P-O2 from 2.6 x 10(-6) to 10 Pa. At low exposures in O-2 (epsilon <= 1- 5 L) an adsorption layer with theta of ca. 0.5 and with the O1s peak at BE = 529.3 eV has been found to form on the surface. When epsilon grows from 5 to 10(8) L, the position and intensity of the oxygen O1s peak remain practically constant. At the same time, as much as 5 mL of oxygen is absorbed according to the TDS data. The results obtained by TDS and XPS indicate that oxygen penetrates deep into the subsurface layers of palladium (>= 15-20 angstrom) and is distributed in its bulk in a low concentration.