Metabolic acidosis is a common complication in patients after kidney transplantation. It is caused by inability of transplanted kidney to regenerate bicarbonate buffer. Although every type of acidosis may be present in these patients, the most frequent are renal tubular acidosis and uremic acidosis. Both insufficiency of graft and tubular dysfunction can be caused by ischemic damage, episodes of rejection and cyclosporine A--induced nephrotoxicity. Ketoacidosis due to a post-transplant diabetes mellitus and bicarbonate loss in patients after simultaneous pancreas/kidney transplantation are rarely observed. Each type of acidosis is responsible for serious metabolic disturbances that influence graft and patient survival. The proper diagnosis and appropriate treatment with oral supplements are essential.