  The hydrogen abundances in DBA white dwarfs determined from optical or UV
spectra have been reported to differ significantly in some studies. We revisit
this problem using our own model atmospheres and synthetic spectra, and present
a theoretical investigation of the Lyman-$\alpha$ line profile as a function of
effective temperature and hydrogen abundance. We identify one possible solution
to this discrepancy and show considerable improvement from a detailed analysis
of optical and UV spectra of DBA stars.
