We propose observations to determine the infrared flux
 density of the supernova remnant 3C58. This is a
 "filled-centre" remnant, with a flat synchrotron spectrum at
 radio wavelengths, but with indications of a spectral
 turnover at wavelengths less than a few mm from the
 available (IRAS) infrared upperlimits. Such a spectral
 turnover is either intrinsic to the emission mechanism at
 work in this object (presumably produced by a central, as
 yet unidentified pulsar: cf. the Crab Nebula), or is due to
 synchrotron losses, with little current energy input. Deeper
 infrared observations will determine the position and form of
 the spectral turnover, which in turn constrains the particle
 acceleration mechanisms at work.