Let (\mathrm{g}) be a finite dimensional complex simple Lie algebra and (U(g)) its enveloping algebra. The quantum group of Drinfeld and Jimbo is a Hopf algebra denoted (U_{q}(\mathbf{g})) defined on Chevalley-like generators over (\mathbb{C}\left[q, q^{-1}\right]). Through "specialization" of (q) at different (\varepsilon \in \mathrm{C}) one obtains a parameterized family of Hopf algebras. When (\varepsilon=1) one recovers the classical universal enveloping algebra. Moreover, when (\varepsilon) is not a root of unity Lusztig (Adv. Math. 70 (1988), 237-249) and Rosso, (Comm. Math. Phys. 117 (1988), 581-593) have shown independently that the representation theory of (U_{\varepsilon}\left(=U_{\varepsilon}(\mathfrak{g})\right)) is analogous to that of (U(\mathfrak{g})). When we fix (\varepsilon) a primitive root of unity the situation changes considerably. At odd roots of unity the representations of (U_{\varepsilon}) are partitioned by conjugacy classes of the algebraic group (G) with Lie algebra (\mathfrak{g}[\mathrm{DC}-\mathrm{K}]). This paper relates the representations of (U_{\varepsilon}) at even roots of unity to conjugacy classes in the group (G^{\vee}-) the Langlands dual of (G). The partition is somewhat finer than that at odd roots of unity and requires a more detailed analysis. This correspondence is then used to study the representations at even roots of unity. In particular, we obtain a "triangulability" result which allows us to calculate the degree of (U_{\varepsilon}) using a deformation argument. (1) 1994 Academic Press, Inc.