Despite the possibility of providing standard collection frameworks, object-oriented languages do not generally encourage a 'very high level' style of programming in which collection components are regarded as first class citizens and in which different implementations for a collection can be exchanged without affecting the correctness of a program and with minimal change to the source code. This results both from weaknesses in the structure of the frameworks and from the poor degree of integration of collections into the languages. In this paper we present a new approach to the integration of collections in object-oriented languages in which collection types are part of the language but collection implementations are not. We also show how the integration of collection types allows automatic conversions which, among other advantages, provide a new solution to the problem of statically type- safe compatibility for collections.