  We have studied the optical spectra of a sample of 31 O- and early B-type
stars in the Small Magellanic Cloud, 21 of which are associated with the young
massive cluster NGC 346. Stellar parameters are determined using an automated
fitting method. Comparison with predictions of stellar evolution that account
for stellar rotation does not result in a unique age, though most stars are
best represented by an age of 1-3 Myr. The present day v_sini distribution of
the 21 dwarf stars in our sample is consistent with an underlying rotational
velocity (v_r) distribution that can be characterised by a mean velocity of
about 160-190 km/s and an effective half width of 100-150 km/s. The v_r
distribution must include a small percentage of slowly rotating stars. If
predictions of the time evolution of the equatorial velocity for massive stars
within the environment of the SMC are correct, the young age of the cluster
implies that this underlying distribution is representative for the initial
rotational velocity distribution. The location in the Hertzsprung-Russell
diagram of the stars showing helium enrichment is in qualitative agreement with
evolutionary tracks accounting for rotation, but not for those ignoring v_r.
The mass loss rates of the SMC objects having luminosities of log L/L_sun > 5.4
are in excellent agreement with predictions. However, for lower luminosity
stars the winds are too weak to determine M_dot accurately from the optical
spectrum. Two of three spectroscopically classified Vz stars from our sample
are located close to the theoretical zero age main sequence, as expected.
