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Development of bronchus-associated lymphoid tissue (BALT) was studied in clinically healthy and diseased Assam local goats. Animals were sacrificed before term as well as at different postnatal periods to screen lung sections for the presence of BALT. In a retrospective study sections prepared from pneumonic lungs were examined for any alteration of BALT. No BALT-like structure was found in neonatal goats. Bronchial lymphoid structures appeared in half of the animals from 1 month of age onward. The frequency of the BALT/4.5 cm2 of lung section ranged from one to two in 1-month-old and three to six in 1-year-old goats. In pneumonic lungs BALT became hyperplastic, and the size was also increased. The incidence of BALT was increased in lungs with fibrotic pneumonia. The number of BALT/section was high (five to eight/4.5-cm2 area) in mesenchymal cell proliferation. The present study shows that BALT did not develop in prenatal periods. But in the presence of potent antigens lymphoid aggregates appeared in the bronchial lamina propria of normal and diseased lungs.