The Molonglo Observatory Synthesis Telescope (MOST), operating at 843 MHz, is currently surveying the southern galactic plane (245° <l<360°, −1.5° ≤b≤ +1.5°). The resulting maps provide images of the radio continuum with a synthesised beamwidth of 43′′ × 43′′ cosec δ and a noise level of about 1mJy. The survey involves 12-hour synthesis observations of over four hundred fields on a predefined set of field centres. About half the fields have been observed to date, and the survey is scheduled for completion in 1990. A noteable feature in many of the fields is the occurrence of widespread diffuse filamentary structure, in addition to the expected supernova remants and HII regions.