Infrared observations of classical novae have established their
 importance as laboratories for studying astrophysical grain
 formation, and as contributors to abundance anomalies in the
 interstellar medium. Studies of abundances in nova ejecta also
 provide information about nucleosynthesis in the white dwarf
 progenitor and in the thermonuclear runaway during a nova explosion.
 Two key, virtually unexplored problems that our proposed ISO
 investigations will address are the documentation of the detailed
 spectral energy distributions and the temporal characteristics of
 classical novae at wavelengths greater than 20 microns. This
 wavelength regime contains many forbidden lines from heavy elements
 that are useful for excitation and abundance studies. Continuum
 emission and broad features at these wavelengths give information
 about dust. Our choice of objects and scientific problems is
 designed to produce an understanding of fundamental differences
 between the early phase of the development of CO and ONeMg novae.

 Specifically, our proposed ISO ToO initiative seeks to
 address five research problems in the study of classical nova
 evolution: 1) chemical abundances of nova ejecta from coronal and
 forbidden emission line spectroscopy; 2) studies of the nature of
 novae in the SMC, LMC, and M31; 3) dynamical studies of nova ejecta;
 4) measurements of the density and masses of the ejecta; and
 5) determinations of the grain size distribution and mineral
 composition of nova dust. The criteria imposed by our science
 objectives in these areas require us to obtain ISO observations
 of novae not contained in the ISO Central Program. Our ISO ToO
 program will be supplemented by supporting observations that our
 ISO team can obtain from ground-based, airborne, and orbiting
 facilities.