A four year (2008-2011) retrospective study of the prevalence of some viral diseases of poultry diagnosed in selected Veterinary clinics in Jos was conducted. A prevalence of 3.0%, 5.7%, and 12.6% (out of a total of 14, 644 cases of poultry diseases) for Newcastle disease (ND), Infectious bursa disease (IBD) and Neoplastic viral diseases (NVD) of poultry respectively were recorded. The prevalence of IBD increased steadily between 2008 and 2011 (1.7%, 4.1%, 7.0%, and 11.6%). This indicates that IBD infection had an average of 3.3% yearly increase of incidence between 2008 and 2011. More so,the prevalence of IBD was found to be higher (9.3%) in broilers and two times more likely to occur than in other type of birds (χ2=215.5; P=0.0001). The prevalence of IBD was also found to be higher (13.7%) and 13.2 times more likely to occur in birds 4-7weeks old than in other age group (χ2=492.8; P=0.0001). The study showed that Newcastle disease was 5.1 times more likely to occur in birds ≥ 20 weeks (χ2=161.4; P=0.0001). Also, neoplastic viral diseases were 12.2 times more likely to occur in birds ≥ 20 weeks. The study also showed that IBD infection peaked in September and November while neoplastic viral diseases occurred on high levels throughout the months between 2008 and 2011. On the other hand ND remained at low levels in all the months between 2008 and 2011. This study therefore recommends that poultry farmers should improve biosecurity and ensure that their birds are vaccinated against these viral diseases.

Keywords: Retrospective, viral, neoplastic, seasonal, biosecurity, diagnosis