We present results from observations obtained with ISOPHOT , on board the ISO satellite Based on observations with ISO , an ESA project with instruments funded by ESA Member States ( especially the PI countries : France , Germany , the Netherlands and the United Kingdom ) with the participation of ISAS and NASA . , of a representative sample of seventeen CSS/GPS radio galaxies and of a control sample of sixteen extended radio galaxies spanning similar ranges in redshift ( 0.2 \leq z \leq 0.8 ) and radio luminosity ( P _ { 2.7 { GHz } } \geq 10 ^ { 26 } W/Hz ) .
The observations have been performed at \lambda = 60 , 90 , 174 and 200 \mu m. The original purpose of these observations was to check whether CSS/GPS sources are associated with very gas rich galaxies , as required by the scenario in which the growth of the radio source is inhibited by the dense medium of the host galaxy .

Unfortunately the resulting performance of ISOPHOT was worse than expected .
As a consequence , the detection limit at 60 \mu m is similar to that obtained previously with IRAS but better than that at 90 \mu m .

Seven of the CSS/GPS sources have detections \geq 3 \sigma at one or more wavelengths , one of which is detected at \geq 5 \sigma .
For the comparison sample five objects have detections \geq 3 \sigma one of which is at \geq 5 \sigma .

By co–adding the data we have obtained average flux densities at the four wavelengths .

We found no evidence that the FIR luminosities of the CSS/GPS sources are significantly different from those of the extended objects and therefore there is not any support for CSS/GPS sources being objects “ frustrated ” by an abnormally dense ambient medium .

The two samples were then combined , providing FIR information on a new sample of radio galaxies at intermediate redshifts .
We compare this information with what previously known from IRAS and discuss the average properties of radio galaxies in the redshift range 0.2 – 0.8 .
The FIR emission can not be accounted for by extrapolation of the synchrotron radio spectrum and we attribute it to thermal dust emission .
The average FIR luminosity is \geq 6 \times 10 ^ { 11 } L _ { \odot } .
Over the observed frequency range the infrared spectrum can be described by a power law with spectral index \alpha \simeq 1.0 \pm 0.2 .
Assuming the emission to be due to dust , a range of temperatures is required , from \geq 80 K to \approx 25 K. The dust masses required to explain the FIR emission range from 5 \times 10 ^ { 5 } ~ { } M _ { \odot } for the hotter component up to 2 \times 10 ^ { 8 } ~ { } M _ { \odot } for the colder one .

We present also observations on four nearby ( z \leq 0.1 ) GPS radio galaxies , two of which are detected at all four wavelengths .