  We find that the local galactic extinction towards the field of gamma-ray
burst GRB970228 is $A_V=1.09^{+0.10}_{-0.20}$, which implies a substantial
dimming and change in the spectral slope of the intrinsic GRB970228 afterglow.
We measure a color $(V_{606}-I_{814})_{ST} = -0.18^{+0.51}_{-0.61}$ for the
extended source coincident with the afterglow. Taking into account our
measurement of the extinction toward this field, this color implies that the
extended source is most likely a galaxy undergoing star formation, in agreement
with our earlier conclusion (\cite{CL98}). In a separate analysis, we find that
the inferred intrinsic spectrum of the GRB 980329 afterglow is consistent with
the predictions of the simplest relativistic fireball model. We also find that
the intrinsic spectrum of the afterglow is extincted both by dust (source frame
$A_V \ga 1$ mag), and that the shape of the extinction curve is typical of
young star-forming regions like the Orion Nebula but is not typical of older
star-forming or starburst regions. The $\approx$ 2 mag drop between the $R$ and
the $I$ bands can be explained by the far-ultraviolet non-linear component of
the extinction curve if $3 \la z \la 4$, and by the 2175 \AA\ bump if $z
\approx 2$; other redshifts are not consistent with the observational data,
given our general model.
