Nocturnal enuresis, defined as intermittent urinary incontinence, regardless of the presence or absence of daytime symptoms, is common. Monosymptomatic nocturnal enuresis – MSNE (no daytime symptoms) has four main causes identified with it: poor vasopressin action, nocturnal polyuria, poor arousal mechanism, poor inhibition of detrusor overactivity at night. Nocturnal polyuria has many possible causes which include abnormal sodium homeostasis, poor vasopressin secretion, abnormal sympathetic – parasympathetic interactions and more recently calcium secretion. The authors of this paper measured 24-hour secretion of urinary calcium in 120 children (age range 7-14) with MSNE, using a control group of 80 ‘dry’ children. Hypercalciuria was found in 23% of children with MSNE compared to 4% of controls. The mean 24-hour urine calcium / body weight ratio was higher in the group with MSNE. A major weakness of the paper was that there was no correlation attempted with diet intake, but several other studies are being published that seem to indicate that calcium excretion has a role to play in nocturnal enuresis. The commonest type of hypercalciuria is ‘idiopathic’ or renal and appropriate management may be considered in such cases.