Between January 1988 and December 1991, 159 patients with Stage III/IV (M0) squamous cell carcinoma of the head and neck were randomized to receive standard fraction RT (70 Gy) (group I) or the same RT plus either 6 mg/m2 of cisplatin (CDPP) (group II) or 25 mg/ m2 of carboplatin (CBDCA) both given daily during RT (group III). Patients in groups II and III had significantly higher overall response rates then those in group I (P = 0.011 and P = 0.0025, respectively) with no difference between groups II and III (P = 0.60). They also had significantly longer median survival time (MST) and higher 5-year survival rates than those in group I (MST, 32 months (32%) and 30 months (29%) versus 16 months (15%), respectively; P = 0.011 and P = 0.019, respectively), with no difference between the two RT/CHT groups. Median time to local recurrence (MTLR) and 5-year local recurrence-free survival (LRFS) were significantly higher for both RT/CHT when compared to RT alone (MTLR, not attained yet and 30 months versus 10 months, respectively; 5-year LRFS, 51% and 48% versus 27%, respectively; P = 0.018 and P = 0.040, respectively) with no difference between the two RT/CHT groups. There was no difference between the three treatment groups regarding regional lymph node and distant metastasis control. Apart from acute high grade (> or =3) hematological toxicity that was significantly more frequent in the two RT/CHT groups and no different between the two RT/CHT groups, other acute high grade toxicity was similar between the three treatment groups. Late high grade toxicity was infrequent and similar between the three treatment groups.