Technical Abstract: Avian Influenza (AI) viruses infect domestic poultry and wild birds. In domestic poultry, AI viruses are typically of low pathogenicity (LP) causing subclinical infections, respiratory disease or drops in egg production. However, a few AI viruses cause severe systemic disease with high mortality; i.e. highly pathogenic (HP)AI. This book chapter provides general information for the veterinary practitioner on etiology, clinical signs, lesions, diagnosis, prevention and contorl of avian influenza in poultry.