The authors describe a case of type 4 renal tubular acidosis, observed in a subject with liver cirrhosis, the pathogenetic cause of which was probably the assumption of spironolactone. It is thought that, even if such an eventuality is not very frequent, it must be considered in clinical practice, in view of the negative consequences that the reduction in urinary ammonium excretion and hyponatriemia, together with this particular form of acidosis, may have on the neurological state of the patients.