The complement system (C) is a major piece of the inflammatory processes triggered after tissue injury. Since implication of the C has been demonstrated during neurodegeneration and Wallerian degeneration, without being clearly explained, we investigated the expression of C4 and clusterin mRNA, at the lesion site, after rat sciatic nerve crush injury. This pilot study was then realized over 28 days during peripheral nerve regeneration. We determined mRNA expression levels in naive control animals (N) and 2, 7, 14 and 28 days (D) after crush experiment, by using semi-quantitative RT-PCR. We observed a basic constitutive expression of both mRNAs in group N. Clusterin mRNA level increased between D2 and D7 to reach 2.5-fold the basic level of expression (N) at D7 and D14, and slightly decreased until D28. C4 mRNA underwent a rapid and marked increase and represented 2-3-fold the N level from D2 to D14, then it decreased until D28 to return to the basic level of expression (N). These preliminary data exhibit very interesting individual variations in mRNA expression and show that a peripheral nerve trauma can stimulate the expression of C4 and clusterin mRNA at the lesion site.