  We examine the prospects for determining $\tan\beta$ from heavy Higgs scalar
production in the minimal supersymmetric standard model at a future $e^+e^-$
collider. Our analysis is independent of assumptions of parameter unification,
and we consider general radiative corrections in the Higgs sector. Bounds are
presented for $\sqrt{s} = 500$ GeV and 1 TeV, several Higgs masses, and a
variety of integrated luminosities. For all cases considered, it is possible to
distinguish low, moderate, and high $\tan\beta$. In addition, we find stringent
constraints for $3\lesssim\tan\beta\lesssim 10$, and, for some scenarios, also
interesting bounds on high $\tan\beta$ through $tbH^{\pm}$ production. Such
measurements may provide strong tests of the Yukawa unifications in grand
unified theories and make possible highly precise determinations of soft SUSY
breaking mass parameters.
