  A composite dust grain model which simultaneously explains the observed
interstellar extinction, polarization, IR emission and the abundance
constraints, is required. We present a composite grain model, which is made up
of a host silicate oblate spheroid and graphite inclusions. The interstellar
extinction curve is evaluated in the spectral region 3.4-0.1$\mu m$ using the
extinction efficiencies of the composite spheroidal grains for three axial
ratios. Extinction curves are computed using the discrete dipole approximation
(DDA). The model curves are subsequently compared with the average observed
interstellar extinction curve and with an extinction curve derived from the IUE
catalogue data.
