Observations have been made to determine the effect of the H II regions on the radio emission from the galaxy. Since both interstellar hydrogen and early-type stars show strong galactic concentration, regions of ionized hydrogen are likely to produce the greatest effect in directions near the galactic equator. At low frequencies, where the “ brightness temperature ” of the general galactic radiation exceeds the kinetic temperature of the interstellar hydrogen, the absorption due to the hydrogen will exceed its emission, and a dark band is to be expected along the galactic equator. At frequencies greater than about 60 Mc/s, where the brightness temperature of the galactic radiation falls below the gas temperature, this band should appear in emission. An interferometric method of large resolving power has been used to determine the distribution of brightness near the galactic plane at frequencies of 81.5 Mc/s and 210 Mc/s. In each case a bright band about 2° wide has been observed superimposed on the general radiation. No accurate observations have yet been made at frequencies less than 60 Mc/s. A comparison of the observed brightness temperature of the band at the two frequencies makes it possible to derive a preliminary estimate of the kinetic temperature and effective density in the H II regions. The temperature derived in this way is considerably greater than the accepted value. Observations at different galactic longitudes have suggested that the distribution of the H II regions shows a marked concentration towards the centre of the galaxy.