N-acetyl D- galactosamine specific jack fruit lectin conjugate was used for the cyto-chemical study of benign and neoplastic lesions of the respiratory tract using diaminobenzidine as substrate on exfoliated cells and tissue sections. Sputum samples from patients with benign respiratory tract lesions (40), squamous cell Carcinoma (20), adenocarcinoma (16), small cell anaplastic carcinoma (12) and large cell anaplastic carcinoma (5) were used for the study. The lectin binding was strong in squamous cell carcinoma, large cell anaplastic carcinoma and adenocarcinoma, but variations in the binding pattern were observed in different carcinoma. Squamous metaplastic cells manifested slightly increased binding to lectin as compared to bronchial and native squamous epithelial cells. The nature of binding was eventually similar in cytology and histology. The ready availability and ease of preparation in purified from makes the jack fruit lectin a potential cytochemical reagent for sputum cytology.