Purpose This Phase III study was performed to determine whether twice-daily (b.i.d.) radiotherapy (RT) resulted in better survival than once-daily (q.d.) RT for patients with limited-stage small-cell lung cancer (LD-SCLC). Methods and materials A total of 310 patients with LD-SCLC initially received three cycles of etoposide and cisplatin. Subsequently, the 261 patients without significant progression were randomized to two cycles of etoposide and cisplatin plus either q.d. RT (50.4 Gy in 28 fractions) or split-course b.i.d. RT (24 Gy in 16 fractions, a 2.5-week break, and 24 Gy in 16 fractions) to the chest. Patients then received a sixth cycle of etoposide and cisplatin followed by prophylactic cranial RT. Results Follow-up ranged from 4.6 to 11.9 years (median, 7.4 years). The median survival and 5-year survival rate from randomization was 20.6 months and 21% for patients who received q.d. RT compared with 20.6 months and 22% for those who received b.i.d. RT (p = 0.68), respectively. No statistically significant differences were found in the rates of progression (p = 0.68), intrathoracic failure (p = 0.45), in-field failure (p = 0.62), or distant failure (p = 0.82) between the two treatment arms. No statistically significant difference was found in the overall rate of Grade 3 or worse (p = 0.83) or Grade 4 or worse toxicity (p = 0.95). Grade 3 or worse esophagitis (p = 0.05) was more common in the b.i.d. arm. Grade 5 toxicity occurred in 4 (3%) of 130 patients who received b.i.d. RT compared with 0 (0%) of 131 who received q.d. RT (p = 0.04). Conclusion Although this study did not demonstrate an advantage to split-course b.i.d. RT, the long-term survival was favorable, likely reflecting the positive influences of concurrent combined modality therapy and prophylactic cranial RT. © 2004 Elsevier Inc.