Intellectual property and the patent system in particular have been extremely present in research and discussion, even in the public media, in the last few years. Without going into any controversial issues regarding the patent system, we approach a very real and growing problem: searching for innovation. The target collection for this task does not consist of patent documents only, but it is in these documents that the main difference is found compared to web or news information retrieval. In addition, the issue of patent search implies a particular user model and search process model. This review is concerned with how research and technology in the field of Information Retrieval assists or even changes the processes of patent search. It is a survey of work done on patent data in relation to Information Retrieval in the last 20–25 years. It explains the sources of difficulty and the existing document processing and retrieval methods of the domain, and provides a motivation for further research in the area.