The present work studies the urinary excretion of PGE2 and PGI2 (6-keto PGF 1 alpha) in 11 insulin-dependent diabetic patients with chronic renal failure with a glomerular filtration rate of 33.9 +/- 9.03 ml/min who had hyporeninaemic hypoaldosteronism to evaluate the influence of these prostaglandins on the appearance of this latter process. The results obtained in this group of patients were compared with those of a control group of healthy individuals, another group of nine non-diabetic patients with CRF, and a last group of eight insulin-dependent diabetic patients with normal renal function to evaluate to what extent the possible variations in prostaglandin excretion could be related to the diabetes, CRF, or a conjunction of both processes. The results of the groups of diabetic patients with CRF were Ccr 33.9 +/- 9.03 ml/min, decreased (P < 0.0001) with respect to the control group and with no difference with the CRF group without diabetes; plasma potassium (4.7 +/- 0.4 mEq/l), increased (P < 0.005) with respect to the values found in the control group; plasma bicarbonate (17.8 +/- 1.8 mEq/l), decreased (P < 0.005) with respect to the control group and also, though not significantly, with respect to the group of non-diabetic patients with CRF. Plasma aldosterone (pg/ml): resting 44.3 +/- 14.9; standing 65.7 +/- 63.5 and post-frusemide 65.5 +/- 58.6, decreased (P < 0.01) with respect to the other three groups. Plasma renin activity (PRA) (ng/ml/h): resting 0.34 +/- 0.3; standing 0.6 +/- 0.4, post-frusemide 0.9 +/- 0.5, decreased significantly with respect to the other three groups.(ABSTRACT TRUNCATED AT 250 WORDS)