  We present a broadband modeling of the afterglow of GRB 021004. The optical
transient of this burst has been detected very early and densely sampled in
several bands. Its light curve shows significant deviations from a simple power
law. We use the data from the X-ray to the $I-$band gathered in the first month
of observations, and examine three models. Two involve variations in the energy
of the shock. The first (energy injection) allows only increases to the shock
energy, while the second (patchy shell) allows the energy to increase or
decrease. In the final model (clumpy medium) the energy of the shock is
constant while the density varies. While all three models reproduce well the
optical bands, the variable density model can best account for the X-ray data,
and the energy-injection model has the poorest fit. None of the models can
account for the modest color variations observed during the first few days of
the burst.
