We previously reported nocturnal plasma IL-1 beta (beta) increases during sleep in absence of stress-induced activation of hypothalamic-pituitary-adrenal (HPA) axis. In this paper we evaluate the presence of plasma IL-1 beta secretion in nine healthy volunteers (mean age 31.2 +/- 4.2) during post-prandial naps, after the administration of zolpidem, a benzodiazepine receptorial agonist. Although a significant increase in IL-1 beta plasma levels during spontaneous sleep was present in only four subjects when compared to those obtained during wake and induced-sleep, spontaneous sleep IL-1 beta mean plasma levels appeared slightly higher than both wake and induced-sleep values. Moreover, a negative correlation was present between IL-1 beta and cortisol (F) values obtained during the early afternoon (r = 7; p < 0.05). Our findings are consistent with a possible association of IL-1 beta secretion to physiologic sleep also during daytime spontaneous naps, with the presence of F influence on this phenomenon, and with the lack of IL-1 beta association to daytime naps after sleep-inducer pharmacological agents.