Effects of universal extra dimensions on Standard Model observables first arise at the oneloop level. The quantization of this class of theories is therefore essential in order to perform predictions. A comprehensive study of the SUC(3)×SUL(2)×UY(1) Standard Model defined in a space-time manifold with one universal extra dimension, compactified on the oribifold S 1 /Z2, is presented. The fact that the four-dimensional Kaluza-Klein theory is subject to two types of gauge transformations is stressed and its quantization under the basis of the BRST symmetry discussed. A SUC(3) × SUL(2) × UY(1)-covariant gauge-fixing procedure for the Kaluza-Klein excitations is introduced. The connection between gauge and mass eigenstate fields is established in an exact way. An exhaustive list of the explicit expressions for all physical couplings induced by the Yang-Mills, Currents, Higgs, and Yukawa sectors is presented. The one-loop renormalizability of the standard Green's functions, which implies that the Standard Model observables do not depend on a cutoff scale, is stressed. subject the KK excitations A (n)a µ [2]. In that paper, we also showed that the SM, or light, Green's functions (Green's functions whose external legs are all zero KK modes or, equivalently, SM fields) are renormalizable at the one-loop level. More recently, this fact was proven explicitly through the direct integration of the heavy KK excitations [3]. The cutoff insensitivity of light Green's functions at the one-loop level, which seems to be exclusive of UED models with one extra dimension, has already been pointed out in previous studies on some electroweak observables [4,5] and verified very recently [6] for the case of one-loop radiative corrections to the trilinear W W γ and W W Z vertices. One peculiarity of UED models is that the tree-level couplings among KK excited modes and zero modes involves strictly two or more KK excitations. This means that the electroweak observables are insensitive to virtual effects of KK excitations at tree level, although they can receive contributions at the one-loop level or higher orders. The main goal of this work is to present a comprehensive study of the vertices involved in the theory, for we think that this important predictive power of UED theories in five dimensions deserves especial attention. This theory would serve as a basis to estimate in an unambiguous way the impact of extra dimensions on electroweak observables. We will present a detailed study of the tree-level structure of the four-dimensional KK theory. Our results comprise a complete list of the Lagrangians characterizing the vertices generated by the compactified theory, including the definition of a gauge-fixing procedure for both the SGT and the NSGT.The rest of the paper has been organized as follows. In Sec. 2, the structure of the five-dimensional SM and the compactification of the extra dimension, including a gauge-fixing procedure, are discussed, whereas, in Sec. 3, a detailed list of the physical vertices of the theory is presented. In ...