  In order to test the unification scheme for double-lobed radio sources, the
far-infrared properties of matched samples of radio-galaxies and radio-loud
quasars were studied using ISOPHOT. The quasar data were complemented with
nearly simultaneous submillimeter and centimeter radio data. The results show
that quasars are generally brighter than radio-galaxies in their far-infrared
output and that beamed non-thermal radiation must be excluded as source for
this infrared excess. However, non-thermal flares or optically thick tori can
still reconcile these results with the unification scheme.
