This study investigated the ability of Borrelia burgdorferi and Borrelia hermsii to attach the surface of several types of in vitro-cultured mammalian cells. Borreliae showed different adhesion efficiencies depending on cell type and temperature. Temperatures both lower and higher than 33 degrees and 37 degrees C respectively, decreased the adhesion of borreliae which preferentially adhere to human fibroblast-like cells. The adhesion process, mediated by structures exposed onto the surface of the microorganisms, also proved to be sensitive to the treatment of mammalian cells with hyaluronidase and sialidase, confirming that carbohydrate receptors are involved in the adhesion of borreliae to eukaryotic cells.