DDAVP is a drug that should be used with caution for each patient individually. Particular care is needed to avoid fluid overload and rapid fluctuations in sodium concentration. Not only families but physicians as well should be educated and aware of the adverse effects of DDAVP, especially in high risk patients. Extreme caution is needed in children with severe neurological and developmental problems who cannot control their fluid intake themselves. Similarly, caution is needed in patients with hypodipsia and DI who have difficulty in balancing water intake and DDAVP dose. The treatment of DI is water; however, DDAVP is given to avoid a large fluid intake which can result in medullary washout. Frequent home monitoring of body weight and regular determinations of serum sodium may help to disclose the early phase of over-hydration or dehydration. DDAVP therapy should be temporarily interrupted during acute illness, febrile episodes, hot days and other conditions with increased water intake. It should be used with considerable caution in patients with cystic fibrosis, or renal or cardiovascular diseases. In patients with enuresis, it is recommended that DDAVP medication should not be continued for longer than 3 months without stopping for 1 week for full reassessment. Fluid intake should be limited 1 hour before and 8 hours after the dose. Generally, undertreatment with vasopressin analogue is safer than overtreatment. A simple measure to avoid overtreatment is to miss one dose once a week; a rapid onset diuresis ('washout' effect) provides considerable reassurance.