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Exposure to light at night (LAN; i.e, light pollution) can interfere with seasonal changes in physiology and behavior in photoperiodic rodents. For example, non-tropical rodents turn off reproduction and bolster immune function in response to short days to improve their odds of winter survival. For Siberian hamsters in particular, dim light at night alters the development of the short-day (winter-like) phenotype and blocks enhanced immune function. The immune and circadian systems are tightly linked. Clock gene expression and their influence on inflammation in peripheral tissues are not well documented. The goal of this study was to explore the underlying gene responses in Siberian hamsters exposed to dim light at night by assaying clock genes and cytokine production in the lymph nodes and spleen. In a full factorial design, Siberian hamsters were exposed to either LD (long day) photoperiods, SD (short day) photoperiods, LD dim light at night (long day dim) photoperiods, and SD dim light at night (short day dim) photoperiods over a period of ten weeks. After extracting RNA from various peripheral organs, lymph nodes, and the spleen, quantitative PCR (qPCR) was performed to analyze gene expression. Dim light at night abolished the short-day body weight, organ mass, and pelage responses in Siberian hamsters. qPCR data and result discussion are forthcoming. Our results may suggest that LAN alters clock gene expression and cytokine production, as well as compromised immune function.