Stringently controlled changes in the local, cytokine-mediated signaling milieu of hair follicles (HF) have been implicated as major elements of hair cycle control and several lines of clinical and experimental evidence point towards interleukin-1 (IL-1) as an important inducer of hair loss. To address the question as to whether the steady state mRNA levels of the gene expression of the IL-1 family parallel distinct phases of the murine hair cycle, we have exploited the high degree of synchrony during depilation-induced HF cycling in mice, and have determined the mRNA levels of IL-1alpha, IL-1beta, IL-1-receptor antagonist, IL-1 receptor (R)-I and IL-1-R-II by semiquantitative RT-PCR. Our results indicate that the induced murine hair cycle is associated with profound fluctuations in the steady state mRNA levels of members of the IL-1 signaling system. Most interestingly, IL-1alpha and IL-1beta transcript levels increased dramatically with the onset of spontaneous catagen (around day 18) and peaked during telogen (day 25). These fluctuations in the IL-1alpha and IL-1beta transcript levels were paralleled by substantial expression changes of the corresponding signal transducing type I IL-1 receptor. Therefore, our findings are consistent with the concept that IL-1alpha, IL-1beta, IL-1-RI and IL-1-RII are involved in the control of catagen development.