SummaryClinical and biological correlations were studied in 16 patients suffering from chronic pyelonephritis. The morphological diagnosis was established12times by renal biopsy and 4 times on surgical or autopsy material.Clinically the salient facts observed were the association of chronic pyelonephritis with diabetes mellitus in 10 cases, the existence of an otherwise unexplained hepatosplenomegaly in 3 cases. Associated hypertension was only found once in the series.Amongst the biological data, an acceleration of the sedimentation rate, an increase of theα2globulien level and a moderate hypochromic anaemia were nearly constantly noted. Renal function revealed variable alterations : Volhard concentration test and phenolsulfonephtalein elimination test were however the most frequently altered. Pyelographies showed delayed elimination for one or both kidneys with more or less modification of the pyelogram.As for the urinary examinations, in all cases, Sternheimer-Malbin pale cells were found and at a minimum concentration of 30 %. It is noticeable that in 3 cases the culture of the urine yielded no germs and that in 2 cases who had had an intensive antibiotherapy the urinary white cells output was not increased.The urine culture obtained 2 hours after renal needle biopsy was positive once in a case where the ordinary methods had shown no bacteria. The culture obtained after dipping the biopsy needle in a bacteriological medium was positive in three cases only.