The circadian system and the stress system each impact an organism’s ability to adapt to environmental challenges (Weibel, Maccari, Van Reeth, 2002). Within the field of circadian studies, much research has been conducted examining the way in which stressors affect clock gene regulation and circadian phenotype. Despite this, very few studies, if any, have looked at the role of early social and environmental impoverishment on circadian phenotype and clock gene expression. As a result, the present study explored whether there was a difference in circadian phenotype and clock gene expression between two groups of rats, one of which had experienced typical early social and physical enrichment, and the other that had been raised in a socially and physically impoverished environment. It was hypothesized that animals that had been raised in an impoverished environment would have a less robust circadian rhythm and be more prone to negative perturbations to both the circadian and stress systems following an acute stressor. Though there was a trend towards significant differences between treatment groups for wheel running behaviours in experiment 1, the only treatment effects found were those of PER1 expression in the amygdala and hippocampus. In experiment 2 a novelty-induced locomotor test was administered to see if the treatment had been effective, and there was a significant main effect of treatment condition. Furthermore, a significant difference between treatment conditions was seen again in the hippocampus. Beyond these treatment effects, there were multiple significant main effects of both sex and ZT for nearly all tests carried out in both experiments.