1-mu m spectroscopy of normal OB stars

We have obtained spectra of 70 normal OB stars in the near-IR I (1-mu m) ba nd. The strongest features are those due to lines of the hydrogen Paschen s eries and neutral and ionized helium, which are, for the most part, in abso rption. The information content in this spectral range is sufficient for on ly a rough classification of hot stars into 'early O', 'late O' and 'B' typ es. Curiously, the leading He I triplet line, He I lambda 1.0830 mu m, is u sually not detectable, although in a few stars it is in emission; its behav iour generally correlates with the leading helium singlet line, He I lambda 2.058 mu m. These two features appear to be present in emission only in st ars with extremes of mass loss or wind extension.