  Big Bang Nucleosynthesis represents perhaps the first, and still perhaps the
most powerful particle-astrophysics connection. As such, it should provide an
example for other work in this area. I discuss the current status of standard
model BBN predictions and constraints, and then argue that the issue of
observational systematic uncertainties is the key feature limiting our ability
to constrain theory with observation. Nevertheless, several very important
constraints are currently obtainable. For example, assuming maximal systematic
uncertainties in $^4$He, D, and $^7$Li we find a conservative upper limit of
$\Omega_B \le 0.16$ in order for BBN predictions to agree with observations.
Equally significant, we find that BBN predictions are inconsistent unless
$^4He$ abundance by mass is greater than $23.9\%$, or D +$^3$He estimates are
incorrect. By contrast, unless systematic uncertainties are taken into account,
the quoted $2\sigma$ observational upper limit on the primordial $^4He$
fraction is $23.8\%$.
