Cyclosporine A is a powerful immunosuppressive agent which is widely used for the prevention of allograft rejection and for the treatment of autoimmune diseases. Clinical and experimental data show that it may also act on connective tissue. We investigated the influence of cyclosporine A on granulation tissue formation and wound healing. Using an in vitro approach, we followed the time course of rat dermal fibroblasts during wound repair. Granulation fibroblasts were compared to dermal fibroblasts flow cytometrically and by mRNA analysis with respect to the expression of procollagen 1 (I), integrin 1, interleukin-6, transforming growth factor 1, keratinocyte growth factor and activin A. The most pronounced effect in cyclosporine-treated rats was the strong down-regulation of activin expression. In cryo-sections of granulation tissue from the same rats, the distribution and expression intensity of intercellular adhesion molecule and its receptors were investigated by immunohistology. Clearly, a time course was detectable. Tissue from CsA-treated animals showed a delay of three days compared to untreated animals. Apoptosis was also delayed in CsA-treated rats by around three days. Furthermore, we investigated the effect of CsA on the expression of collagen 1 (I), fibronectin and matrix metalloprotease 1 genes in dermal fibroblasts from untreated donors. No changes in the mRNA steady state levels of these genes were revealed after direct addition of different doses of CsA to fibroblast cultures. Our data suggest that CsA may interfere with the complicated net of interactions between connective tissue and the immune system by down-regulation of the inflammatory phase by modulation of cytokines and a subsequent delay of tissue repair.