1 The identification and investigation of novel clock-controlled genes (CCGs) has been conducted 2 thus far mainly in model organisms such as nocturnal rodents, with limited information in 3 humans. Here, we aimed to characterize daily and circadian expression rhythms of CCGs in 4 human peripheral blood during a sleep/sleep deprivation (S/SD) study and a constant routine 5 7 in the S/SD study, and across 33 h in 12 participants in the CR study. Statistically significant 8 rhythms in expression were observed for STAT3, SREBF1, TRIB1, and THRA1 in samples from 9 both the S/SD and the CR studies, indicating that their rhythmicity is driven by the endogenous 10 clock. The MKNK2 gene was significantly rhythmic in the S/SD but not the CR study, which 11 implies it's exogenously-driven rhythmic expression. Additionally, we confirmed the circadian 12 expression of PER1, PER3, and REV-ERBα in the CR study samples, while BMAL1 and 13 HSPA1B were not significantly rhythmic in the CR samples; all five genes previously showed 14 significant expression in the S/SD study samples. Overall, our results demonstrate that rhythmic 15 expression patterns of clock and selected clock-controlled genes in human blood cells are in part 16 determined by exogenous factors (sleep and fasting state) and in part by the endogenous 17 circadian timing system. Knowledge of the exogenous and endogenous regulation of gene 18 expression rhythms is needed prior to the selection of potential candidate marker genes for future 19 applications in medical and forensic settings.