This study examined the impact of fluctuating thermal regimes (FTRs) on cold tolerance of the polyphagous beetle Alphitobius diaperinus. Daily pulses of elevated temperatures can provide breaks in chronic cold stress, potentially allowing for physiological recovery and improving survival. Perturbations in central metabolism appear to be a common physiological response in insects exposed to low temperatures. It has been suggested that energy supplies, which may be depleted during cold exposure, can be regenerated during the warming pulses of FTRs. This study tested the assumption that chronic cold stress may induce ATP depletion and that recovery during FTR warming pulses may allow re-establishment of ATP supplies. In this study, A. diaperinus were exposed to cold stress under different thermal regimes (constant or fluctuating). The results did not confirm the aforementioned assumption. No cold-induced ATP depletion was observed. The lowest ATP levels were repeatedly detected in the untreated controls. The data show that homoeostasis of ATP is lost when adults A. diaperinus are exposed to cold stress, whatever thermal regime (constant or fluctuating). ATP accumulation may be viewed as a symptom of a production/consumption imbalance under cold stress conditions. Periodic short (2-h) warming pulses clearly improved cold survival. Cellular homeostasis, however, probably requires a longer recovery period to be fully restored. © 2011 Elsevier Inc.