  We describe the first lattice determination of the strong coupling constant
with 3 flavors of dynamical quarks. The method follows previous analyses in
using a perturbative expansion for the plaquette and Upsilon spectroscopy to
set the scale. Using dynamical configurations from the MILC collaboration with
2+1 flavors of dynamical quarks we are able to avoid previous problems of
having to extrapolate to 3 light flavors from 0 and 2. Our results agree with
our previous work: alpha_s_MSbar(M_Z) = 0.121(3).
