['Empirical evidence suggests that autocrine human GH (hGH) may possess a proliferative and oncogenic role in human mammary carcinoma. However, this concept is largely derived from studies using cultured human mammary carcinoma cell (HMCC) lines.', 'We investigated the expression and functionality of hGH and the hGH receptor in isolated cultures of primary HMCC.', 'Epithelial cell adhesion molecule-positive primary HMCC were isolated from surgical biopsies of patients with mammary carcinoma and cultured in vitro. Expression of hGH and hGH receptor was determined by RT-PCR, immunofluorescence microscopy, and ELISA. The proliferative response of the cultured primary HMCC to hGH stimulation or hGH inhibition with a hGH antagonist was determined.', 'One hundred percent of cultured primary HMCC expressed the hGH receptor, and 52% expressed hGH at the mRNA level. hGH-positive primary HMCC produced hGH protein within the cell and secreted hGH to the media. Both hGH-negative and hGH-positive HMCC responded to hGH stimulation with large increases in cell number. hGH-positive HMCC responded to inhibition of hGH by a hGH antagonist with a decrease in cell number, whereas hGH-negative HMCC did not.'] Are autocrine proliferative effects of hGH maintained in primary cultures of human mammary carcinoma cells?