The ability of the kidney to acidify urine is modulated by aldosterone. Acquired or inborn defects associated with aldosterone insufficiency result in a form of hyperkalemic distal renal tubular acidosis (type IV dRTA). However, all animal models have been based on adrenalectomy which also affects a number of other hormones involved in acid-base homeostasis. Here we examined a mouse model lacking aldosterone synthase (AS KO) catalyzing the final step in aldosterone synthesis. AS KO have a lower blood pH, lower bicarbonate and chloride level as well as mild hyperkalemia. These changes were accompanied by a higher urine output, a more alkaline urine, increased water and food intake. In the kidney absence of aldosterone lead to increased expression of acid-base transportes such as AE1 and pendrin. Our results suggest that mice lacking aldosterone synthase have symptoms of dRTA type IV and therefore may serve as a model of investigating this disease. Furthermore, our results demonstrate that pendrin expression is not primarily regulated by aldosterone as postulated.