This chapter addresses the issue of determining the response time distribution in networks of queues. Four different techniques are described and demonstrated. A two-step numerical approach to compute the response time distribution for closed Markovian networks with general connectivity, a technique for determining the approximate (exact under certain conditions) response time distribution of a time Markov chain (CTMC) "response time blocks," an expansion of "response time blocks" to open Markovian networks with general phase-type (PH) service time distributions, and an approach for handling non-Markovian networks having M/G/1 priority and PH/G/1 queues. These techniques are shown to give accurate results with much smaller CTMCs or semi-Markov processes than exact analysis.