Abstract. Partial or complete spontaneous cancer regression is a rare phenomenon, particularly in patients with lung cancer. This is the case report of a patient with lung cancer who exhibited spontaneous regression of the primary as well as metastatic lesions, without receiving any treatment. Spontaneous regression commenced within a week of obtaining pathological specimens by transbronchial and percutaneous biopsies from the primary lesion and metastatic lymph nodes of the left side of the neck. The reason for this phenomenon is unknown; however, we hypothesized that there may be an immunological association between the stimulus of the biopsies and the spontaneous regression. This patient should be closely followed up to monitor the clinical course of this unusual case.