A multicenter and retrospective study of the diagnosis value of SCC-TA4 in squamous cell carcinomas of 4 localisations was made with the 2 thresholds of 2 and 2.5 ng/ml. However, 3.1% of controls have a SCC value above 2.5 ng/ml. Sixteen benign gynecologic pathologies had no positive level. The benign digestive (N = 73), bronchial (N = 345) pathologies and no squamous cell carcinomas (N = 93, N = 220 respectively), had SCC-TA4 mean levels significantly lower than corresponding squamous cell carcinomas (N = 153, N = 128 respectively). Sensitivity of the test varied from 40% in the squamous cell carcinomas of the lung, to 72% in the squamous cell carcinomas of the uterine cervix. Specificity was always very high and varied from 91% in the SCC of lung, to 100% in the SCC of uterine cervix. For the SCC of uterine cervix, oesophagus and head and neck, the mean values and incidence of positive levels increased significantly with increasing tumor size and advancing disease stage. For the SCC of uterine cervix, mean SCC-TA4 levels and percentages of positive levels above 2 ng/ml were significantly higher for the patients with recurrence (22.5 +/- 4.6 ng/ml; 76%) or with metastasis appearance (23.6 +/- 5.4 ng/ml; 77%) than for the patients in remission (less than 1.5 ng/ml; 0%). In the SCC of oesophagus, we report levels before treatment that are significantly higher for the patients with metastasis at the first attempt (4.2 +/- 5.1 ng/ml; 59%), and an elevated SCC level at the diagnosis evoked a SCC of lung already disseminated (8.8 +/- 12.1 ng/ml; 50%) that will fail to respond to treatment (4.0 +/- 4.2 ng/ml; 48%).