- Willi-Prader syndrome (hypogenital dystrophy with diabetic tendency) 759.81
- Willis' disease (diabetes mellitus) (see also Diabetes) 250.0
- Wilms' tumor or neoplasm (nephroblastoma) (M8960/3) 189.0
- Wilson's
- Wilson-Brocq disease (dermatitis exfoliativa) 695.89
- Wilson-Mikity syndrome 770.7
- Window - see also Imperfect, closure aorticopulmonary 745.0
- Winged scapula 736.89
- Winter - see also condition
- Wise's disease 696.2
- Wiskott-Aldrich syndrome (eczema-thrombocytopenia) 279.12
- Withdrawal symptoms, syndrome
- Withdrawing reaction, child or adolescent 313.22
- Witts' anemia (achlorhydric anemia) 280.9
- Witzelsucht 301.9
- Woakes' syndrome (ethmoiditis) 471.1
- Wohlfart-Kugelberg-Welander disease 335.11
- Woillez's disease (acute idiopathic pulmonary congestion) 518.52
- Wolff-Parkinson-White syndrome (anomalous atrioventricular excitation) 426.7
- Wolhynian fever 083.1
- Wolman's disease (primary familial xanthomatosis) 272.7
- Wood asthma 495.8