The bromine content of human gliomas and white matter was determined by neutron activation analysis (NAA) following p.o. administration of a single dose of 400-500 mg/m2 dibromodulcitol (DBD). In another group of patients with brain gliomas, the bromine content was measured subsequent to application of a single dose of 334 mg/m2 of sodium bromide (equivalent dose regarding the bromine content of DBD). The bromine content of these two groups was compared to the values found in a third control group of untreated patients. The amount of bromine after DBD application was three to four times higher than in the untreated samples and the average accumulation ratio of 1.8 +/- 0.4 proved to be nearly identical both in tumour and white matter. The bromine values after NaBr treatment showed a different pattern of distribution. The accumulation was higher in the tumour tissue than in the normal white matter. These findings demonstrate that the pharmacokinetic properties of DBD- and NaBr-derived bromine are different, suggesting that the increase of bromine after DBD administration could be due to covalently bound bromine in DBD.