In a system including a collection of cooperating cache servers, such as proxy cache servers, a request can be forwarded to a cooperating cache server if the requested object cannot be found locally. An overload condition is detected if for example, due to reference skew, some objects are in high demand by all the clients and the cache servers that contain those hot objects become overloaded due to forwarded requests. In response, the load is balanced by shifting some or all of the forwarded requests from an overloaded cache server to a less loaded one. Both centralized and distributed load balancing environments are described.