  We present spectral analysis of early observations of the Type IIn supernova
1998S using the general non-local thermodynamic equilibrium atmosphere code \tt
PHOENIX}. We model both the underlying supernova spectrum and the overlying
circumstellar interaction region and produce spectra in good agreement with
observations. The early spectra are well fit by lines produced primarily in the
circumstellar region itself, and later spectra are due primarily to the
supernova ejecta. Intermediate spectra are affected by both regions. A
mass-loss rate of order $\dot M \sim 0.0001-0.001$\msol yr$^{-1}$ is inferred
for a wind speed of 100-1000 \kmps. We discuss how future self-consistent
models will better clarify the underlying progenitor structure.
