Heat stress caused by high temperature events significantly reduces grain yield and quality worldwide, especially those occur at reproductive tissue developmental stages of cereal crops. Although high temperatures affect both male and female tissue developments, it is the male reproductive tissues that are most sensitive to high temperatures. In this study, we performed a time course heat stress study to examine the effects of high temperature on gene expression at early developmental stages of tassel development in maize. RNA-seq was used for the genome-wide gene expression analysis. Gene expression difference between tassel tissues of heat-stressed and non-stressed control plants at set developmental stages and gene expression pattern differences in heat-stressed and non-stressed control plants over different tassel developmental stages are being analyzed and will be reported.