Patients taking anticonvulsant drugs display a broad spectrum of side-effects. Particularly, in the beginning of treatment and with increasing doses of carbamazepine, side effects such as dizziness, ataxia, drowsiness and reduction of alertness occur, which improve some days after the dose has reached a stable level. Our aim was to find objective parameters for grading these side effects and to differentiate between neurophysiological and neuropsychological side effects of carbamazepine in a clinical situation. Twenty-two patients with trigeminal neuralgia were included for a follow-up study with increasing carbamazepine doses (0 mg to 600 mg). The effect of carbamazepine on postural stability was quantified by posturography. Different neuropsychological tests to study cognitive effects of carbamazepine were performed. The composite equilibrium score showed a significant reduction of postural stability with increasing doses of carbamazepine. In sensory analysis the somatosensory ratio was significantly influenced by increased doses of carbamazepine during the study. Mean reaction time of tonic alertness and physical alertness varied significantly with different doses of carbamazepine. There was a significant influence in patients attention during trail making tests and divided attention tests with increase in carbamazepine. In conclusion our observations show that the rate of change of carbamazepine doses is an important determinant of cognitive and motor functions in the phase of increasing doses.