Galectins are a family of animal beta-galactoside-binding lectins involved in malignant transformation and progression. The present study evaluated the immunohistochemical expression of galectin-3 in a consecutive series of 81 radically resected non-small cell lung carcinomas (NSCLCs). The main pattern of galectin-3 expression was cytoplasmic (median percentage of cells with cytoplasmic positivity: 80.0%). The median percentage of tumor cells with nuclear and cytoplasmic co-expression of galectin-3 was 3.5%. No cases with exclusive nuclear immunostaining were observed. Functional interaction between galectin-3 and the thyroid transcription factor-1 (TTF-1) was previously demonstrated by cotransfection experiments. In the present study, concomitant expression of nuclear galectin-3 and TTF-1 was independently associated with a worse clinical outcome (HR 2.0; P = 0.01).