Ultraviolet Spectra of Stars: The ultraviolet spectra of stars are discussed from both theoretical and observational viewpoints.

According to theories of model stellar atmospheres only stars of spectral types from O to about B3 may be expected to be bright in the ultraviolet-wavelength region. Observations of the strong resonance lines between 911.6 and 1900 A will yield new information permitting construction of better models for the outermost layers of OB stars. However, an adequate theory of line-formation, including non-l.t.e. effects, should be used if an accurate physical representation is to result. Already it has been demonstrated beyond doubt that O and B0 supergiants are surrounded by expanding atmospheres.