Linear polarization of dust emission has been mapped around the star f
orming cloud cores W3 IRS5 and rho Oph SM1, at a wavelength of 800 mum
. In the former source the data are consistent with magnetic field lin
es that converge on the central object, whereas in the latter the fiel
d lines appear close to parallel. The results are consistent with a cu
rrent model of star formation in high-mass and low-mass cores, but the
presence of other nearby sources, and an outflow in W3 IRS5, could af
fect this interpretation.