The MessageAmp II-Biotin Enhanced Kit uses the T7 linear amplification method commonly referred to as the Eberwine method (Van Gelder et al. 1990) to amplify RNA from a total or mRNA sample in a way that most accurately represents the initial mRNA profile. This amplified RNA is most commonly used for subsequent microarray profiling. The kit provides a complete system for generating biotinylated, amplified RNA, which has been optimized for hybridization with Affymetrix GeneChip?arrays. An NTP mix containing biotinylated UTP has been added to the kit for ease of use and optimal labeling. Optimization that has occurred with incorporating biotin labeling into the kit has significantly increased array data sensitivity, providing users with increased Percent Present Calls and sufficient amounts of amplified RNA for array analysis after just a single round of amplification using only 50 ng of input RNA (Figure 1). The kit includes enough reagents for the single-round amplification and biotin-labeling of 20 samples.