The purpose was to analyze survival and its predicting factors in differentiated thyroid carcinoma (DTC) patients with distant metastases (M1). Radioiodine ((131)I) therapy was performed in 363 DTC patients from 1977 to 2000. Among 75 patients, 44 patients had M1 at the time of initial therapy and 31 patients had M1, which developed during the follow up. The probability of survival and its predicting factors were tested by Kaplan-Meier's method. Seventy five DTC patients with M1 included 49 (65.3%) women and 26 (34.7%) men; 30 (40%) patients were < 45 years old and 45 (60%) patients were >or= 45 years old (range 8-70 years; mean age = 45.5 years); 52 papillary carcinomas, 22 follicular carcinomas, and one inconclusive finding. Probability of survival after appearance of M1 was 60.7% at 5 years, 51.2% at 10, and 38.4% at 15 and 20 years. Some predicting factors showed significant influence on the survival: age (p = 0.0001), histological type (p = 0.0138), and initial therapy (p = 0.0351), while gender had no influence (p = 0.2046). We can conclude that patients' age, histopathology of the tumor, and initial therapy significantly influence the survival. Longer survival of DTC patients with M1 could be achieved by adequate surgery followed by 131I therapy.