  The presence of magnetic fields in O-type stars has been suspected for a long
time. The discovery of such fields would explain a wide range of well
documented enigmatic phenomena in massive stars, in particular cyclical wind
variability, Halpha emission variations, chemical peculiarity, narrow X-ray
emission lines and non-thermal radio/X-ray emission. Here we present the
results of our studies of magnetic fields in O-type stars, carried out over the
last years.
