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 Coratelli Shaul G. Massry TUBULO-INTERSTITIAL NEPHROPATHIES 1 STRUCTURAL, ASPECTS OF THE RENAL INTERSTITIUM W.KRIZ AND K.V. LEMLEY Institute of Anatomy and Cell Biology, University of Heidelberg, D-6900 Heidelberg 1, F.R.G. Childrens Hospital of Los Angeles, Division of Nephrology, Los Angeles, U.S.A. The interstitium of the kidney includes the extravascular inter- tubular spaces of" the renal parenchyma, with their attendant cellular elements and extracellular substances. It is bounded on all sides by tubular and vascular basement membranes. The lymphatics are considered as part of the interstitium.

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 Coratelli Shaul G. Massry TUBULO-INTERSTITIAL NEPHROPATHIES 1 STRUCTURAL, ASPECTS OF THE RENAL INTERSTITIUM W.KRIZ AND K.V. LEMLEY Institute of Anatomy and Cell Biology, University of Heidelberg, D-6900 Heidelberg 1, F.R.G. Childrens Hospital of Los Angeles, Division of Nephrology, Los Angeles, U.S.A. The interstitium of the kidney includes the extravascular inter- tubular spaces of" the renal parenchyma, with their attendant cellular elements and extracellular substances. It is bounded on all sides by tubular and vascular basement membranes. The lymphatics are considered as part of the interstitium.