We investigated the time course of central disease recurrence (CDR) in 2997 patients treated with radiation for stage I-II squamous cell carcinoma of the cervix. CDR rates were 6.8%, 7.8%, and 9.6%, at 5, 10, and 20 years, respectively. The risk of CDR was independently correlated with tumor size (P < 0.0001) but not with FIGO stage. The hazard rate peaked in the first year of follow-up and then fell steeply; after 3 years, the hazard rate was approximately constant at 0.2-0.4% per year. Although after 3 years the risk of CDR was low, it continued to be slightly greater for patients with tumors > or =5 cm than for those with smaller tumors (P= 0.001). Patients who had CDR < 36 months after treatment were less likely to be candidates for salvage therapy and had a poorer post-recurrence survival rate than those with recurrence > or =36 months after treatment (4.5% versus 42.1%, P < 0.0001). The higher rate of CDR in the first 3 years and the poor survival after early recurrence suggest that most early CDRs are true relapses. The relatively stable annual actuarial risk between 3 and 25 years and the better survival rate after late CDR suggest that most "recurrences" after 3 years are actually new neoplasms.