Observation of biomolecular interactions at the single-molecule level reveals kinetic information crucial for understanding biophysical processes and provide the basis for a new class of molecular diagnostics based on time-domain analysis of molecular interactions. Point-functionalized carbon nanotubes, otherwise known as single-molecule field-effect transistors (smFETs), have shown significant advantage over fluorescence-based approaches for such single-molecule applications due to their high measurement bandwidths, virtually unlimited observation times, low cost, and capabilities for integration with CMOS in large arrays. Here, we demonstrate the capabilities of single-molecule field-effect transistors to measure DNA hybridization kinetics and to selectively detect small molecules through conformational changes of a single-stranded DNA aptamer. In both cases, kinetics can also be modified electrostatically by changes in the bias between the smFET and the surrounding electrolyte.