Quantified parameters of photically evoked afterdischarge and EEG background activity of visual cortex of freely moving rats were used as variables to obtain a t profile for each drug dosage. Behavioural scores were also used. The determination of the dose/time-effect profile of a compound was based on normalization of data and on calculation of the first two factor values in comparison with pooled data of representatives of neuroleptic, anxiolytic, convulsant, petit mal anticonvulsant, antidepressant and psychostimulant drug classes. The compounds were investigated in different dosages and/or routes of administration. The model and procedure are validated for antipsychotic, anxiolytic and vigilance enhancer effect, and comprise the predictability of proconvulsive and petit mal anticonvulsive effects.