This study describes the use of microarrays to monitor gene expression in human T cells, specifically focusing on the heat shock response and phorbol ester signaling. The authors prepared microarrays containing 1046 human cDNAs and used them to quantitatively analyze gene expression under different conditions. The microarrays were highly sensitive, detecting differential expression patterns in 95% of the array elements. The study identified 17 genes with altered expression in heat-shocked cells, 11 of which were induced and 6 repressed. Sequencing of these genes revealed known heat shock proteins and novel sequences. Similarly, six genes were identified as being induced by phorbol ester treatment, including *PAC-1* and *NF-κB1*. The microarray method was also applied to human tissues, showing consistent expression patterns across different tissue types. The study highlights the potential of microarrays for large-scale gene discovery and functional analysis, emphasizing their advantages over other high-capacity expression analysis methods.This study describes the use of microarrays to monitor gene expression in human T cells, specifically focusing on the heat shock response and phorbol ester signaling. The authors prepared microarrays containing 1046 human cDNAs and used them to quantitatively analyze gene expression under different conditions. The microarrays were highly sensitive, detecting differential expression patterns in 95% of the array elements. The study identified 17 genes with altered expression in heat-shocked cells, 11 of which were induced and 6 repressed. Sequencing of these genes revealed known heat shock proteins and novel sequences. Similarly, six genes were identified as being induced by phorbol ester treatment, including *PAC-1* and *NF-κB1*. The microarray method was also applied to human tissues, showing consistent expression patterns across different tissue types. The study highlights the potential of microarrays for large-scale gene discovery and functional analysis, emphasizing their advantages over other high-capacity expression analysis methods.