  The two leading models for the structure of GRB jets are the uniform jet
model and the universal structured jet (USJ) model. In the latter, all GRB jets
are intrinsically identical and the energy per solid angle drops as the inverse
square of the angle from the jet axis. The simplicity of the USJ model gives it
a strong predictive power, including a specific prediction for the observed GRB
distribution as a function of both the redshift $z$ and the viewing angle
$\theta$. We show that the current sample of GRBs with known $z$ and estimated
$\theta$ does not agree with the predictions of the USJ model. This can be best
seen for a relatively narrow range in $z$, in which the USJ model predicts that
most GRBs should be near the upper end of the observed range in $\theta$, while
in the observed sample most GRBs are near the lower end of that range. Since
the current sample is very inhomogeneous (i.e. involves many different
detectors), it should be taken with care and cannot be used to rule out the USJ
model. Nevertheless, this sample strongly disfavors the USJ model. Comparing
the prediction for the observed GRB distribution both in $\theta$ and in $z$,
with a larger and more homogeneous GRB sample, like the one expected from
Swift, would either clearly rule out the USJ model, or alternatively, provide a
strong support for it. The test presented here is general, and can be used to
test any model that predicts both a luminosity function and a luminosity-angle
relation.
