  We perform a phenomenological analysis of neutrino oscillation in a four
generation framework introducing an additional sterile neutrino. In such a
scenario, more than one pattern is possible that can accommodate three
hieararchically different mass squared differences as required by the present
experiments. We considered two different spectrums. Choosing the
${\Delta{m}}^2$s in the ranges suitable for the LSND, atmospheric and solar
neutrino oscillation, limits on the mixing angles are derived, consistent with
the most restrictive accelerator and reactor data as well as the atmospheric
and solar neutrino results. The allowed mixing angles are found to be
constrained very severely in both cases. For one mass pattern in the combined
allowed zone the atmospheric anomaly can be explained by $\nu_e - \nu_{\mu}$
oscillation whereas for the other the $\nu_{\mu} - \nu_{\tau}$ channel is
preferred. The accelerator experiments CHORUS and NOMAD have different
sensitivities in these regions and they can distinguish between the two
choices.
