We were awarded 41 hours of Priority 3 time for this proposal in the first ISO call, and we are here requesting that this priority, for a sub-sample of 50 galaxies of our original sample which reside in the deep field of the survey, be upgraded. We propose to carry out far-infrared observations of a complete and homogeneous sample of 50 galaxies selected in radio (1.4 GHz) wavelengths to a flux limit of S(1.4) 0.3 mJy, covering a sub-area of 0.5 square degree of our original survey. To this limit, a significant number of ultra-luminous infrared galaxies and Seyferts are expected to be detected. We propose to investigate if the absence of high-redshift galaxies from deep optical surveys is due to dust extinction of starforming ellipticals. Also, Far-infrared observations will be used to estimate the space densities of different classes of objects in deep radio surveys and to investigate if the radio-60 micron relation, found for local galaxies, holds for the fainter, more distant sources as well. Nature of the excess population, detected in in optical and far-infrared surveys will also be studied.