Sleep is highly conserved across taxa, and thought to be crucial for life. The suite of genetic factors that contribute to variation in sleep in natural populations, however, remains unknown. We conducted an artificial selection study coupled with RNA-Seq in order to identify gene networks associated with phenotypic changes over time. Using a previously created outbred population of flies constructed from ten Drosophila Genetic Reference Panel lines having extreme long and short night sleep duration, we constructed six selection populations. Two populations were designated as short-sleeper populations, two as long-sleeper populations, and two populations served as an unselected control. Each generation, we assayed sleep in each population. We chose the 25% most extreme sleepers as parents for the subsequent generation in the short- and long- sleeper populations; we chose 25% of the flies at random to be parents in the subsequent generation of controls. After 13 generations of selection, night sleep duration in the long-sleeper populations averaged 642.2 ± 3.83 and 667.8 ± 2.97 minutes; 104.3 ± 6.71 and 156.2 ± 8.76 minutes in the short-sleeper populations; and 563.4 ± 7.62 and 542.3 ± 7.91 minutes in the control populations. Night and day average bout length and sleep latency exhibited a correlated response to selection for night sleep across generations, while night and day bout number, day sleep, and waking activity did not. We harvested total RNA from homogenates of 10 flies of each sex per generation and sequenced poly-A selected libraries. We are currently analyzing the sequence data to detect patterns of expression across selection scheme, sex, and generation. Our goal is to detect gene expression networks that are crucial to these phenotypic changes.