In the present work, the effect of surface treatment methods on the henequen fiber topography and how the surface treatment influences the interfacial shear strength of henequen/unsaturated polyester composites were studied. Two different surface treatment methods were used: soaking method and ultrasonic method. Two different treatment media were used: normal tap water and sodium hydroxide. The result showed that the topography of henequen fiber surfaces was greatly changed, strongly depending oil the treatment method and media used. It was demonstrated from the single fiber microbonding test result that the interfacial shear strength (IFSS) between the natural fibers and the matrix of henequen/unsaturated polyester composites was significantly improved by the surface treatments of henequen prior to composite preparation. The topological and interfacial results were quite consistent with each other. (C) Koninklijke Brill NV, Leiden, 2009