In human dermal fibroblasts, brought to quiescence (G(0)) by serum starvation, the S phase peaked 24 h and G(2)/M phases 36 h after serum re-addition, Under the same conditions, ornithine decarboxylase mRNA peaked at 12 h, decreased markedly in S phase and remained low until 48 h, Conversely, ornithine decarboxylase antizyme transcript dropped to its lowest level at 12 h, while reaching its highest values between 24 and 48 h. Ornithine decarboxylase activity followed essentially the pattern of its mRNA, but relative changes were much greater, S-Adenosylmethionine decarboxylase transcript and enzyme activity also peaked at around 12 h, decreasing thereafter, Spermidine/spermine N-1-acetyltransferase mRNA and activity reached the highest values at 36-48 h, Putrescine concentration increased up to 18 h and fell dramatically in the S phase, remaining low thereafter. Both spermidine and spermine reached peaks at 18 h and decreased in the S phase, but not nearly as much as putrescine, We discuss hom this comprehensive study may help Co understand the involvement of polyamines in the control of cell proliferation, (C) 1999 Federation of European Biochemical Societies.