Biosensors are now a well-established technology in the study of small molecules.  This talk will focus on several aspects of this type of work that biosensor users can be expected to explain.  These are: A) Describing Mass Transport: Mass transport is a common phenomenon in biosensor data that can affect the uniqueness of solutions derived from fits.  The origins of mass transport will be described as well as how mass transport has been modeled quantitatively to help explain the lack of uniqueness in solutions.   How mass transport manifests itself with respect to the shape of sensorgrams will also be described. B)  Reproducibility of Biosensor Data: Biosensors are commonly used to derive rate and equilibrium constants for molecular interactions.  Many of these values appear in publications and technical reports.  A commonly asked question about this technology relates to the magnitude of experimental errors that can typically be expected.  Some case examples will be discussed to help orient the audience as to the reliability of values of cited. C) Problematic Data:   Several case examples of actual problematic data that has been collected will be presented.  The dilemma that some of these data sets can pose in their interpretation will be discussed.