Introduction. Infants with urinary tract malformations (UTM) presenting with urinary tract infection (UTI) are prone to develop transient type 1 pseudohypoaldosteronism (THPA1). Objective. Report on patient series with characteristics of THPA1, UTM and/or UTI and suggestions for the diagnosis and therapy. Methods. Patients underwent blood and urine electrolyte and acid-base analysis, serum aldosterosterone levels and plasma rennin activity measuring; urinalysis, urinoculture and renal ultrasound were done and medical and/or surgical therapy was instituted. Results. Hyponatraemia (120.9?5.8 mmol/L), hyperkalaemia (6.9?0.9 mmol/L), metabolic acidosis (plasma bicarbonate, 11?1.4 mmol/L), and a rise in serum creatinine levels (145?101 ?mol/L) were associated with inappropriately high urinary sodium (51.3?17.5 mmol/L) and low potassium (14.1?5.9 mmol/L) excretion. Elevated plasma aldosterone concentrations (170.4?100.5 ng/dL) and the very high levels of the plasma aldosterone to potassium ratio (25.2?15.6) together with diminished urinary K/Na values (0.31?0.19) indicated tubular resistance to aldosterone. After institution of appropriate medical and/or surgical therapy, serum electrolytes, creatinine, and acid-base balance were normalized. Imaging studies showed ureteropyelic or ureterovesical junction obstruction in 3 and 2 patients, respectively, posterior urethral valves in 3, and normal UT in 1 patient. According to our knowledge, this is the first report on THPA1 in the Serbian literature. Conclusion. Male infants with hyponatraemia, hyperkalaemia and metabolic acidosis have to have their urine examined and the renal ultrasound has to be done in order to avoid both, the underdiagnosis of THPA1 and the inappropriate medication.