To investigate the presence of messenger RNA (mRNA) encoding insulin-like growth factor binding proteins (IGPBP) in human secretory endometrial stromal cells cultured in vitro, total cellular mRNA and protein extracted from cells treated with various hormones were detected and identified by Northern and Western blotting techniques respectively. Northern blot analysis detected 1.4 and 2.5 kilobase (kb) mRNA transcripts for IGFBP-2 and IGFBP-3 respectively, in both control and progestin-treated secretory human endometrial stromal cells in vitro. However, the 1.5 kb mRNA transcript of IGFBP-1 was detected only in progestin-treated cells but not in the controls. Progestin alone markedly stimulated cellular BP-1 protein and mRNA, but only moderately stimulated cellular IGFBP-2 and IGFBP-3 protein mRNA in a dose-dependent fashion. Adding relaxin at the same time as progestin further enhanced the stimulatory effects of progesterone. Oestradiol had a stimulatory effect on cellular IGFBP-2 mRNA, but had an inhibitory effect on protein and mRNA of IGFBP-3, also in a dose-dependent fashion. In general, for each specific binding protein, the amount of cellular mRNA correlated well with the amount of cellular protein. Therefore, IGFBP protein and mRNA transcript in human secretory endometrial stromal cells appears to be under hormonal influence. These hormones may control the synthesis of IGFBPs at the transcription rather than the translation level.