Scientists routinely talk and write about gene expression and the abundance of transcripts, but in reality they extrapolate this information from the various measurements that a variety of different technologies provide. Indeed, there are many reasons why applying different technologies to the problem of transcript abundance may give different results, owing to an incomplete understanding of the gene in question or from shortcomings in the applications of the technologies. There are nine basic considerations for making a technology choice for quantitating gene expression that will impact the overall outcome: architecture, specificity, sensitivity, sample requirement, coverage, throughput, cost, reproducibility, and data management. These considerations will be discussed in the context of available technologies.