We have identified the cell types expressing SOCS and CIS mRNA, and quantified the relative levels of expression in human breast tumours of increasing severity from a preinvasive stage (ductal carcinoma) to invasive carcinoma, for which we have previously documented the gene expression levels for both GH and PRL receptors (Mertani et al, 1998). This evidence concerns the gene CISH and in situ carcinoma.