  We investigate the notion of conditionally positive definite in the context
of Hilbert $C^*$-modules and present a characterization of the conditionally
positive definiteness in terms of the usual positive definiteness. We give a
Kolmogorov type representation of conditionally positive definite kernels in
Hilbert $C^*$-modules. As a consequence, we show that a $C^*$-metric space $(S,
d)$ is $C^*$-isometric to a subset of a Hilbert $C^*$-module if and only if
$K(s,t)=-d(s,t)^2$ is a conditionally positive definite kernel. We also present
a characterization of the order $K'\leq K$ between conditionally positive
definite kernels.
