We measured the adsorption of water vapor and trinitrotoluene (TNT) on a silicon cantilever that was coated with a self-assembled monolayer (SAM) of 4-mercaptobenzoic acid on one surface. Even though hydrogen bonding is responsible for adsorption in both cases, the adsorption characteristics were quite different for the two species. In the case of water vapor, the mass loading and bending both increased with relative humidity in a linear fashion. For TNT in the dry nitrogen carrier, the mass loading and bending initially increased rapidly and then leveled off around one monolayer of coverage irrespective of the TNT concentration. This study shows that microcantilevers provide a convenient and versatile platform for the monitoring of molecular binding to SAMs.