A new type of middle‐infrared optical fiber is proposed in which oxide glass is used as the cladding material to define a hollow core. Several kinds of oxide glasses have refractive indices lower than unity in the frequency range near 1000 cm−1due to the nearby reasonance of molecular vibration; hence due to the total reflection of the incident laser light from air to the oxide‐glass surface, it is expected that the hollow‐core optical fiber made with the glass functioning as the cladding will exhibit small transmission loss. A preliminary experiment on a 1‐mm‐inner diam hollow‐core Pb glass optical fiber shows its loss to be 7.7 dB/m at 940 cm−1for CO2laser light.