This paper studies the change-point problem and the cross-covariance functi
on for ARCH models. Bounds for the cross-covariance function are derived an
d explicit formulae are obtained in special cases. Consistency of a CUSUM t
ype change-point estimator is proved and its rate of convergence is establi
shed. A Hajek-Renyi type inequality is also proved. Results are obtained un
der weak moment assumptions.