Some carbohydrates are known to decrease the attachment of Acanthamoeba sp. to biological surfaces. By a method based on the reduction of a tetrazolium salt (XTT) by the mitochondrial dehydrogenases of the parasites, d-mannose and alpha-d-mannopyranoside have been shown to reduce Acanthamoeba attachment to inert surfaces, indicating that the mannose binding protein of Acanthamoeba trophozoites is involved in adherence to inert surfaces. The reduction in attachment is dose dependant and is not linked with a potential toxicity of the carbohydrates. All the species of Acanthamoeba tested were concerned by this mannose binding protein, but the adhesion of A. culbertsoni was also reduced by the presence of glucose.