This document describes a recommended methodology for modeling and measuring the performance of slave stratum clock equipment in telecommunication networks. A slave clock is a clock whose timing output is controlled by the timing signal received from a clock of equal or higher quality. A slave clock unit consists of a timing ensemble of oscillators@ and a servo mechanism to control and monitor the timing performance of the oscillators with respect to the timing reference. This methodology has been developed by the T1X1.3 Synchronization Working Group of ANSI accredited committee T1 Telecommunications based on an ongoing study of the performance of slave clocks in actual network environments. It is recognized that current slave clock standards are not adequate to ensure acceptable network timing performance. The methodology presented here is expected to be the basis of enhancing the current stratum clock specifications in ANSI T1.101-1987 Synchronization Interface Standards for Digital Networks.