  The most direct experimental signature of a compactified extra dimension is
the appearance of towers of Kaluza-Klein particles obeying specific mass and
coupling relations. However, such masses and couplings are subject to radiative
corrections. In this paper, using techniques developed in previous work, we
investigate the extent to which such radiative corrections deform the expected
tree-level relations between Kaluza-Klein masses and couplings. As toy models
for our analysis, we investigate a flat five-dimensional scalar \lambda\phi^4
model and a flat five-dimensional Yukawa model involving both scalars and
fermions. In each case, we identify the conditions under which the tree-level
relations are stable to one-loop order, and the situations in which radiative
corrections modify the algebraic forms of these relations. Such corrections to
Kaluza-Klein spectra therefore have the potential to distort the apparent
geometry of a large extra dimension.
