Collibacillosis, one of the common bacterial diseases, is a burning problem for the poultry raiser as well as to consumers. Collibacillosis refers to any localized or systemic infections caused entirely or partly by avian pathogenic E. coli (APEC.Symptoms observed may be colisepticemia, coligarnuloma, air sacculities, coliform salphingitis, omphalitis, cellulities, coliform peritonitis, synovitis and panopthalmitis. Collectively, the infections caused by E. coli are responsible for significant loss in productivity of both broilers and layers. In broilers, collibacillosis has been found responsible for low rate of performances, weight loss, low FCR and mortality. The rising phenomenon of multiple resistances represents a worldwide problem for Veterinary and public health sectors.This book elaborates the scenario of National Avian Laboratory Chitwan, some clinical cases and moreover an extensive study about antibiotic sensitivity of E coli isolated from broiler of Chitwan, Nepal.