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We have studied the optical spectra of a sample of 31 O- and early B-typestars in the Small Magellanic Cloud, 21 of which are associated with the youngmassive cluster NGC 346. Stellar parameters are determined using an automatedfitting method. Comparison with predictions of stellar evolution that accountfor stellar rotation does not result in a unique age, though most stars arebest represented by an age of 1-3 Myr. The present day v_sini distribution ofthe 21 dwarf stars in our sample is consistent with an underlying rotationalvelocity (v_r) distribution that can be characterised by a mean velocity ofabout 160-190 km/s and an effective half width of 100-150 km/s. The v_rdistribution must include a small percentage of slowly rotating stars. Ifpredictions of the time evolution of the equatorial velocity for massive starswithin the environment of the SMC are correct, the young age of the clusterimplies that this underlying distribution is representative for the initialrotational velocity distribution. The location in the Hertzsprung-Russelldiagram of the stars showing helium enrichment is in qualitative agreement withevolutionary 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 > 5.4are in excellent agreement with predictions. However, for lower luminositystars the winds are too weak to determine M_dot accurately from the opticalspectrum. Two of three spectroscopically classified Vz stars from our sampleare located close to the theoretical zero age main sequence, as expected.Comment: 35 pages, accepted for publication in A&

The VLT-FLAMES survey of massive stars: mass loss and rotation of early-type stars in the SMC