Boron abundances have been derived for seven main sequence B-type stars from HST STIS spectra around the \ion B3 2066Å line .
In two stars , boron appears to be undepleted with respect to the presumed initial abundance .
In one star , boron is detectable but it is clearly depleted .
In the other four stars , boron is undetectable implying depletions of 1 to 2 dex .
Three of these four stars are nitrogen enriched , but the fourth shows no enrichment of nitrogen .
Only rotationally induced mixing predicts that boron depletions are unaccompanied by nitrogen enrichments .
The inferred rate of boron depletion from our observations is in good agreement with these predictions .
Other boron-depleted nitrogen-normal stars are identified from the literature .
Also , several boron-depleted nitrogen-rich stars are identified , and while all fall on the boron-nitrogen trend predicted by rotationally-induced mixing , a majority have nitrogen enrichments that are not uniquely explained by rotation .

The spectra have also been used to determine iron-group ( Cr , Mn , Fe , and Ni ) abundances .
The seven B-type stars have near solar iron-group abundances , as expected for young stars in the solar neighborhood .
We have also analysed the halo B-type star , PG 0832+676 .
We find [ Fe/H ] = - 0.88 \pm 0.10 , and the absence of the \ion B3 line gives the upper limit [ B/H ] < - 2.5 .
These and other published abundances are used to infer the star ’ s evolutionary status as a post-AGB star .