A longitudinal study of circulating immune complexes (CIC), cancer antigen 125 (CA125), carcinoembryonic antigen (CEA) and a sub-fraction of the TA-4 squamous cell carcinoma tumor-associated antigen (SCC) has been undertaken in 38 patients with cervical carcinoma. Pre- and post-treatment values have been compared with those obtained in well-defined clinical remission and relapse phases of their disease. Each tumor marker was assessed in terms of "lead time" before clinically obvious recurrent disease became evident. The data from the four subjects with adenocarcinoma of the cervix gave equivocal results and no firm conclusions could be drawn. However, for the 34 patients with squamous cell carcinoma the medium value (data was skewed) for SCC was elevated above normal in the presenting pretreatment sera (4.5 ng/ml) and significantly fell to 2.5 ng/ml post-treatment (P less than 0.01). A similar pattern was not apparent for CIC, CEA, or CA125 data. When results were examined for an individual patient, of those with recurrent squamous cell lesions who died, 12/24 demonstrated elevated, and rising SCC values before clinical evidence of the disease and a further 6 (25%) at the time recurrence was clinically evident. This information gave lead times of between 2 and 52 months (median 13 months) for 75% of patients. Only 1 subject had values which remained in the normal range (less than 2 ng/ml) even though their disease was progressive. Similarly of the subjects still in clinical remission 8/9 had values within the normal range. The data for CIC, CA125, and CEA were not individually useful as a marker. Furthermore, combining the data from all analytes to give a panel of potential markers did not improve the prognosis already evident with SCC alone. It has therefore been concluded that SCC is a useful biochemical marker of the progression of squamous cell carcinoma of the cervix.