Leptospirosis is an important global human and veterinary health problem. Humans can be infected by exposure to chronically infected animals and their environment. An important focus of the current leptospiral research is the identification of outer membrane proteins (OMPs). Due to their location, leptospiral OMPs are likely to be relevant in host-pathogen interactions, hence their potential ability to stimulate heterologous immunity. The existing whole-genome sequence of <i>Leptospira interrogans</i> serovar Copenhageni offers a unique opportunity to search for cell surface proteins. Predicted genes encoding potential surface proteins were amplified from genomic DNA by PCR methodology and cloned into an <i>Escherichia coli</i> expression system. The partially purified recombinant proteins were probed by Western blotting with sera from human patients diagnosed with leptospirosis. Sixteen proteins, out of a hundred tested, were recognized by antibodies present in human sera. Four of these proteins were conserved among eight serovars of <i>L. interrogans</i> and absent in the non-pathogenic <i>Leptospira biflexa</i>. These proteins might be useful for the diagnosis of the disease as well as potential vaccine candidates.Facultad de Ciencias ExactasInstituto de Biotecnologia y Biologia Molecular