The radio source 3C 272.1, associated with the elliptical galaxy M84 in the Virgo cluster, has been observed at 2·7 and 5·0 GHz with half-power beam widths of |${12}^{\prime{}\prime}\times{52}^{\prime{}\prime}$| arc and |${6}^{\prime{}\prime}\cdot5\times{28}^{\prime{}\prime}$| arc respectively. The maps obtained show that the source has a spiral structure. Linear polarization of up to 20 per cent in places has been found, consistent with a magnetic field predominantly perpendicular to the axis of the spiral.