Infectious and non-infectious tubulointerstitial nephropathies are old subjects but there is enough confusion and disagreement on terminology and etiopathogenesis to warrant a new look at these problems. We were fortunate in having at the Pediatric Nephrology Seminar 6 and as contributors to this volume, the representative- or shall I say "originators"? - of each of the three most identifi- able positions: Dr. Renee Habib - congenital anomalies, Dr. John Hodson - reflux, and Dr. Robert Heptinstall - infection. Although some tend to hold onto one position and exclude others, in this case there was overlapping of perception. Dr. Habib accepts a role for infection in reflux and for infection in the presence of obstruc- tion; Dr. Hodson accepts infection and congenital anomalies as modi- fiers; and Dr. Heptinstall takes an overall position whicm encompas- ses the three. Thus the first part of the book emphasizes the complexity of something as seemingly simple as UTI and demonstrates awareness of disagreement even among the pros about meanings, interpretations, and treatment. Drs. Gustavo Gordillo, Jorge de la Cruz and their associates emphasize the importance of predisposing factors for UTI; Dr. Materson focuses on the workup of the patient, Dr. Zillerueloon bacteriological aspects, and Dr. Gorman on treatment approaches. Dr. Vaamonde reviews nephrotoxic agents. Finally, Drs. Andres and Noble review the immunological aspects of various tubulointer- stitial nephritides.