  We present a parsec-scale image of the OH maser in the nucleus of the active
galaxy IIIZw35, made using the Very Long Baseline Array at a wavelength of 18
cm. We detected two distinct components, with a projected separation of 50 pc
(for D=110 Mpc) and a separation in Doppler velocity of 70 km/s, which contain
50% of the total maser flux. Velocity gradients within these components could
indicate rotation of clouds with binding mass densities of ~7000 solar masses
per cubic parsec, or total masses of more than 500,000 solar masses. Emission
in the 1665-MHz OH line is roughly coincident in position with that in the
1667-MHz line, although the lines peak at different Doppler velocities. We
detected no 18 cm continuum emission; our upper limit implies a peak apparent
optical depth greater than 3.4, assuming the maser is an unsaturated amplifier
of continuum radiation.
