Between January 1988 and December 1991, 159 patients with Stage III/IV (MO) 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/m(2) of cisplatin (CDPP) (group II) or 25 mg/m(2) 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 (greater than or equal to 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. (C) 1997 Elsevier Science Ireland Ltd.