Human chorionic gonadotropin (hCG)-like molecules have been reported to be elevated in a substantial fraction of serum samples from patients with various gynaecologic tumours and have been discussed as possible markers in these malignancies. Employing highly sensitive and specific immunoradiometric assays, we determined total hCG-related immunoreactivity (hCG/hCG beta), as well as free alpha-subunit (alpha-SU), common to all glycoprotein hormones, in serum (n = 106) and malignant effusions (n = 26) of women with gynaecologic malignancies. For comparison, we also measured hCG/hCG beta in nonmalignant ascitic fluids (n = 21). HCG/hCG beta serum levels were elevated (> 5 IU L-1) in 39 of 106 patients (37%) with gynaecologic malignancies, whereas free alpha-SU was above normal range only in seven (6.6%). Frequencies of hCG/hCG beta elevations were similar in women with endometrial, (n = 39), cervical (n = 40) and ovarian (n = 27) cancer, being 30%, 35% and 41%, respectively. In malignant ascites (n = 15) and tumour cyst fluids (n = 11) of patients with ovarian cancer, hCG/hCG beta concentrations were significantly higher than in the corresponding serum samples and benign ascitic samples. Free alpha-SU, on the other hand, was increased in only one of 26 malignant effusions. In conclusion, hCG/hCG beta is frequently elevated in serum of patients with endometrial, cervical and ovarian cancer and may serve as a tumour marker in these malignancies, particularly in patients where other markers are negative. In this respect, analysis of ascitic or tumour cyst fluids may be of higher diagnostic value as serum measurements.