Hypertrophic pulmonary osteoarthropathy (HPO) associated with non-small cell lung cancer in a 58-year-old man was accompanied by an elevated serum level of growth hormone (GH). HPO rapidly disappeared after resection of the primary tumor and the elevation of serum GH was resolved. Immunohistochemically the tumor contained growth hormone-releasing hormone (GHRH) but not GH. These findings suggest that the high serum GH level due to ectopic GHRH production in the tumor, was a contributing factor in HPO. This is the second reported case of non-small cell lung cancer which was immunohistochemically positive for GHRH associated with HPO.