Human blood platelets are intimately involved in the regulation of thrombosis, inflammation, and wound repair. These cells retain megakaryocyte-derived cytoplasmic mRNA and functionally intact protein translational capabilities, although very little is known about normal or pathological mRNA profiles. Microarray analysis has demonstrated a clear and reproducible molecular signature unique to platelets. There is a relative paucity of expressed transcripts compared with those found in other eukaryotic cells, most likely related to mRNA decay in these anucleate cells. In contrast, a complementary methodology for transcript profiling (serial analysis of gene expression [SAGE]) demonstrates that 89% of tags represent mitochondrial (mt) transcripts (enriched in 16S and 12S ribosomal RNAs), presumably related to persistent mt-transcription in the absence of nuclear-derived transcripts. The abundance of nonmitochondrial SAGE tags parallels relative expression for the most abundant transcripts as determined by microarray analysis, establishing the concordance of both techniques for platelet profiling. These observations establish the validity of transcript analysis as a tool for identifying novel platelet genes that may regulate normal and pathologic platelet (and/or megakaryocyte) functions. The potential application of platelet-specific microarrays in scientific and clinical settings related to platelet production, cardiovascular, and cerebrovascular diseases is reviewed.