We are pleased to present to our readers the proceedings of the Fourth Bari Seminars in Nephrology. The Topic of these proceedings deals with tubulo interstitial nephropathies. The Bari Seminars in nephrology are bi-annual meetings attended by a large international audience comprised of clinician-scientists in the various disci plines of nephrology and related fields. We trust that our readers will find the content of these proceedings reward ing and interesting. We are indebted for the generous financial support of the Centro Nationale delle Richerche, Italy. Alberto Amerio Pasquale...