Progressive Multifocal Leukoencephalopathy (PML) is a demyelinating disease of the central nervous system. It is characterized by widespread lesions caused due to lytic infection of the oligodendrocytes by John Cunningham Virus (JCV), especially in immunocompromi sed individuals. We report a case of a 36 year old man, a known HIV positive case on Anti-Retroviral Therapy (ART) for 15 years,who was admitted to a tertiary care hospital in Tamil Nadu, South India with history of difficulty in walking,weakness and pain of the lower limbs, involuntary micturition, intermittent altered sensorium, loss of weight and appetite. He was diagnosed to have PML through neuro-imaging studies,serum JC viral antibodies assay and cerebrospinal fluid JCV real time polymerase chain reaction (PCR) assay. We report this rare case of PML in view of its potential interest and we also review literature regarding its etiopathogenesis, diagnosis and management.