Congenital nephrogenic diabetes insipidus is characterized by insensitivity of the distal nephron to arginine vasopressin. Clinical knowledge of this disease is based largely on case reports. For this study, data were collected on clinical presentation and during long-term follow-up of 30 male patients with congenital nephrogenic diabetes insipidus. The majority of patients (87%) were diagnosed within the first 2.5 yr of life. Main symptoms at clinical presentation were vomiting and anorexia, failure to thrive, fever, and constipation. Three older patients were diagnosed as a result of events not directly related to the disease. Except for a possibly milder phenotype in patients with a G185C mutation, no clear relationship between clinical and genetic data could be found. Most patients were on hydrochlorothiazide-amiloride treatment without significant side effects. Two patients suffered from severe hydronephrosis with a small rupture of the urinary tract after a minor trauma, and two patients experienced episodes of acute urine retention. Height SD scores for age remained below the 50th percentile in the majority of patients, whereas weight for height SD scores showed a catch-up after several years of underweight.