Observations of 22 DB stars using theuvbyphotometric system are discussed. In the [(b–y),(u–b)] diagram, these objects define a relatively tight sequence, but the interpretation is hampered by the lack of a precise knowledge of atmospheric element abundances in these stars. The recent models of Koester (1979) show a larger gravity separation for the DB's using Strömgren photometry and appear to fit the observations better than earlier theoretical results. Due to the tightness of the DB sequence

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... at the hot and cool ends, respectively, there appears to be evidence for restricted ranges in loggand the atmospheric hydrogen abundance.