Tumour tissue levels of platinum were determined in patients with head and neck tumours receiving carboplatin (11 patients, 400 mg/m2) and iproplatin (5 patients, 360 mg/m2). The platinum concentrations ranged from 1.1 +/- 0.4 ng Pt/mg tissue (iproplatin administration) to 1.4 +/- 0.3 ng Pt/mg tissue (carboplatin administration). These results were compared with published platinum levels after cisplatin administration. Although the administered dose of carboplatin (1.08 mmol/m2) and iproplatin (0.86 mmol/m2) was higher than the cisplatin one (0.33 mmol/m2), no significant statistical differences were observed in the resulting platinum tissue levels. The constancy of tumour platinum level after treatment with different platinum complexes could be explained, at least for carboplatin and cisplatin, by both the tumour diffusion properties and the reactivity of the drugs.