What is ISI and why is it important?

In March 2000 the senior editor of ISI (Institute of Scientific Information) informed the Survey Review that it had been decided to index the journal as part of the ISI product range, commencing with the January 2000 issue. This generated the response amongst the Editorial Board "I think that this is positive, but does anybody know what this means?" The aim of this short review is to demonstrate that this development is indeed positive and to clarify why. I was asked to write this article because I had supported Keith Atkinson in the successful campaign to get the Photogrammetric Record re-instated in early 1999 and I had raised the issue at the Teachers of Surveying conference held in 1998. The article will outline the philosophy behind ISI and review the recent Web of Science product, before attempting to answer why inclusion in the ISI membership is important, particularly for academic readers.