Pleural effusions are commonly encountered in the clinical practise of both respiratory and nonrespiratory specialists. An estimated 1–1.5 million new cases in the USA and 200?000–250?000 new cases of pleural effusions are reported from the UK each year [1]. Analysis of the relevant clinical history, physical examination, chest radiography and diagnostic thoracentesis is useful in identifying the cause of pleural effusion in majority of the cases [2]. In a few cases, the aetiology may be unclear after the initial assessment. The list of diseases that may account for a persistent undiagnosed pleural effusion is long [3]. We present an interesting case of undiagnosed pleural effusion that was encountered in our hospital.