Abstract
Cytological examination of the pleural effusion fluid obtained from a 66-yr-old Chinese lady showed numerous intra-and intracytoplasmic colourless refractile non-birefringent crystals. X-ray analysis of the crystals identified barium salts. On further inquiry, it was learnt that the fluid obtained had been placed in a specimen bottle provided by the x–ray department. This container was presumably contaminated with barium salts. The case highlights an unusual aspect of specimen contamination and the usefulness of x-ray analysis in the identification of crystals/substances.