The main approaches used by the Laboratory for Biological Mass Spectrometry include: Intact protein molecular weight determination; identification of proteins from simple and complex mixtures; metabolomics; quantitative analysis; post-translational modification characterization; protein-protein interaction mapping via chemical crosslinking. In this presentation, I will discuss practical considerations regarding sample analysis and the types of data we can generate. I will highlight results of some recent collaborations to illustrate the range of biological problems for which mass spectrometry can provide important insight into the underlying biology.