Tracheobronchial lymphadenomegaly is commonly associated with lymphosarcoma and disseminated mycotic infection. Available data also suggest other pathologic causes of enlarged tracheobronchial lymph nodes. Our objective was to establish the distribution and prevalence of diseases that cause radiographically evident tracheobronchial lymphadenomegaly in a large population of dogs. Patients were divided into groups based on the methods of diagnoses with 25 having confirmed diagnoses and 85 with presumptive diagnoses. Of the 110 dogs in the study, 92 (84%) had neoplasia and 18 (16%) had infectious diseases. Infections were attributed to Coccidioides (12, 67%), Aspergillus (3, 17%), and 1 each (6%) to Nocardia, Penicillium, and Mycobacteriosis. Tumors were characterized as lymphoma (66, 60%) or nonlymphoid (26, 23.6%). Nonlymphomas in Group 1 included histiocytic sarcoma complex (16%), carcinoma (12%), adenocarcinoma (8%), osteosarcoma (8%), chemodectoma (4%), ganglioneuroblastoma (4%), and neuroendocrine (4%). The number of dogs with tracheobronchial lymphadenomegaly scores 1, 2, 3, 4, or 5 (with 5 being the greatest) was 8 (7%), 15 (14%), 30 (27%), 15 (14%), and 44 (38%), respectively. The results suggest that in addition to diagnoses of lymphoma and fungal infections, other neoplasms and in particular histiocytic sarcoma and metastatic adenocarcinoma, should be considered when tracheobronchial lymphadenomegaly is identified radiographically in dogs. When comparing the degree of tracheobronchial lymphadenopathy by disease category, there was no significant affiliation (P = 0.33).