An unusual case of primary mediastinal tuberculous abscess is presented in whom the diagnosis was obtained on magnetic resonance (MR) and ultrasound (US) guided aspiration cytology. Mycobacterium tuberculosis was isolated from direct smear as well as from culture of the "pus". Normal spine signal with MR and normal bone scintigraphy excluded any vertebral focus of infection. MR was helpful in, defining the extent and characterising the abscess, besides excluding a vertebral focus of infection.