Outbreaks of infectious laryngotracheitis (ILT) were diagnosed in cross- bred (6-10 weeks of age) and broiler breeder chickens (19-20 weeks of age) with mortality rates ranged from 4.4‌12.5% and 1.5-2 % per week, respectively. Four field isolates of laryngotracheitis virus (LTV) were recovered from suspensions of pooled tracheas of affected flock after 1-2 serial passages into 10- day-old specific-pathogen-free (SPF) chicken embryos,and were identified by agar gel precipitation test (AGPT) using reference mono-specific LTV antiserum. In addition, the pathogenicity study of LTV which isolated from crossbred chickens, in 50- day- old cross- bred chickens and in chicken embryos revealed that this isolate Was a virulent strain based on intratracheal Pathogenicity index (ITPI), tracheal lesion scores and mortality index for chicken embryos (MICE). Assessment of protection against this isolate using either chicken embryo origin (CEO) or tissue culture origin (TCO) vaccines revealed that chickens receiving two vaccinations had lower lesion scores and higher ELISA antibody titers than those vaccinated once. These results suggest that a priming vaccination followed by a booster dose offers better protection against circulated wild virulent LT than a single vaccination alone, moreover, the epizootiology of the disease was discussed.