Background: Endosonography (EUS) guided FNA is a relatively new imaging modality which is increasingly used for sampling deep-seated lymph nodes in the diagnosis and staging of various malignancies, both primary as well as metastatic. It is also useful for staging of non-Hodgkin's lymphoma as well as diagnosing recurrence. The diagnosis of leukemia on FNA samples from deep-seated lymphadenopathy poses an even greater challenge. Hairy cell leukemia (HCL) is an uncommon, but distinct, lympho-proliferative disorder of B cell origin. It usually affects the spleen and bone marrow and uncommonly involves lymph nodes. There are only a few cases reported where HCL was diagnosed on FNA specimens. Case presentation: We report the first case of HCL accurately rendered on EUS-FNA samples. Conclusion: This report underscores the concept that the presence of a cytopathologist in the endoscopy suite plays an important role in providing accurate diagnoses of lymphoid lesions biopsied with EUS-FNA. © 2006 Meara et al; licensee BioMed Central Ltd.