We report the expression and characterization of the omp52 gene of Leptospira santarosai serovar Shermani strain CCF that is isolated in Taiwan. omp52 was identified among pathogenic leptospires but not among non-pathogenic leptospires by using suppression subtractive hybridization in our previous study. With an open reading frame of 1371 bp that encodes 456 amino acids and a predicted molecular mass of 52.6 kDa, Omp52 was shown to be an outer membrane protein containing a C-terminal OmpA consensus domain and exposed on the cell surface. Furthermore, Omp52 increases dramatically during the stationary phase, indicating that the expression of Omp52 is environmentally regulated. By using immunoblotting analysis, we proved that Omp52 was expressed in human patients infected with leptospires. These observations suggest that Omp52 may play roles in the interaction of host cells and pathogens during infection.