Secretoglobin (SCGB) 3A2 is a downstream target gene for the thyroid transcription factor-1 (TITF1). SCGB3A2 plays a role as an anti-inflammatory agent, however, its role in primary pulmonary carcinomas has not been examined. We assessed immunohistochemical expression of SCGB3A2 in primary pulmonary carcinomas and evaluated the correlation between the expression and histopathological phenotypes and prognosis. One hundred and fifty-six primary lung cancers undergone for surgical resection were examined. The percentages of SCGB3A2 positive cells were scored and tumors had immunoreactivity in more than 10% of tumor cells were considered positive for SCGB3A2. Overall reactivity for SCGB3A2 was observed in 116 (74.4%) of 156 primary lung cancers. SCGB3A2 was predominantly expressed in adenocarcinomas (86.5%), compared with squamous cell carcinomas (50.0%) and small cell carcinomas (42.9%). The expression in papillary adenocarcinomas was seen at higher frequency than that in tubular adenocarcinomas. There was no significant relationship between SCGB3A2 expression and tumor differentiation, and pathological stage. Positive expression of SCGB3A2 was not associated with better survival rate. SCGB3A2 expression in primary pulmonary carcinomas is high, especially in adenocarcinomas. Our results indicate that SCGB3A2 has a potential to be a specific and useful marker for primary pulmonary adenocarcinomas.