UIP is a histological term adopted to describe a pattern of interstitial fibrosis characterized by peripheral and basal interstitial fibrosis and presence of honeycombing cysts. If no cause is identified this is known as idiopathic pulmonary fibrosis (IPF). Alternatively UIP pattern can be observed in several endstage fibrotic lung disease including collagen vascular disease, asbestosis, hypersensitivity pneumonitis, sarcoidosis and drug reaction. If HRCT finding is equivocal biopsy maybe required to distinguish UIP from fibrotic non specific interstitial pneumonia (NSIP).