The co-expression of M-CSF (CSF-1) and its receptor in specimens of ovarian cancer has recently been reported. Preliminary results have already suggested a possible influence of steroids on FMS (M-CSF receptor) expression. Fifty-five non-pretreated FIGO stage III/IV ovarian adenocarcinomas were studied for M-CSF transcripts and protein, as well as FMS transcripts and protein, using standard molecular biological techniques (Northern blot, slot blot analysis) and immunocytochemistry (ICC). Steroid receptor content was measured by DCC analysis in 44/55 specimens; in addition, ER/PR (oestrogen/progesterone) ICC was performed in 32/55 specimens. All tumours were shown to contain M-CSF-specific mRNA. Likewise, M-CSF protein was detected by ICC in the stroma and over the epithelium in all specimens. However, while most tumours were shown to contain FMS-specific mRNA, only 64 per cent of cases showed significant expression of FMS protein by tumour epithelium as shown by ICC. A statistically significant positive correlation was found between M-CSF and FMS mRNA expression levels. A week non-significant positive correlation was noted between FMS mRNA expression levels and tumour grade. Carcinomas were ER-positive in 66 per cent (DCC) or 34 per cent (ICC), and PR-positive in 73 per cent (DCC) or 34 per cent (ICC). A statistically significant positive correlation between ER (DCC) and M-CSF mRNA expression levels was found. Weak non-significant correlations were present between ER (ICC) and FMS (ICC), as well as between PR (DCC) and FMS mRNA expression.(ABSTRACT TRUNCATED AT 250 WORDS)