The transcriptome is the mRNA pool found within a cell. Transcriptomic discovery approaches include microarray-based technologies as well as sequencing-based technologies. Transcriptomic experiments provide dynamic information about gene expression at the tissue level. The proteome is the pool of proteins expressed at a given time and circumstance. The word PROTEOMICS summarizes several technologies for visualization, quantitation, and identification of these proteins. Protein separation can be accomplished by two-dimensional electrophoresis, use of protein chips with an affinity matrix, or by a variety of advanced chromatographic methods. Mass spectrometry is used to identify the proteins in conjunction with protein sequence databases. Recent proteomic experiments in resting and activated platelets have identified novel signaling pathways and secreted proteins. Platelet transcriptomic studies in essential thrombocythemia, atherosclerotic disease, sickle cell disease, and an inherited platelet defect are reviewed. Transcript profiling has the potential to distinguish molecular signatures in normal and diseased platelets and to classify prothrombotic patient phenotypes to tailor their therapy.