A low molecular weight glycoprotein immunologically identical with the beta-core fragment of hCG (beta C-hCG) has been described in invasive tumors of the genital tract, particularly carcinoma of the cervix. A previous report has also suggested increased urinary concentrations in subjects with cervical intraepithelial neoplasia (CIN). This prospective study of 107 patients with CIN was conducted to determine concentrations of beta C-hCG in the urine compared to a reference population without CIN. All subjects underwent a cervical smear and colposcopy, with biopsy when indicated. Between 11 and 18% of patients had urinary concentrations of beta C-hCG greater than the upper limit of the reference group and these results were confirmed when corrected for urinary creatinine concentration. A substantial number of subjects (19%) also had a positive result in a C-terminal immunoassay. It is concluded that preinvasive carcinoma of the cervix may secrete hCG or beta C-hCG in the earliest stages although measurement of beta C-hCG is unlikely to prove to be a valuable diagnostic marker in CIN.