There is both pharmacological and clinical support for a classification of the schizophrenic syndrome into negative and positive subtypes. For neuroleptics that act upon both types of symptoms, it appears that lower doses are required for treatment of negative than for positive symptoms. Successful drug treatment of negative symptoms may therefore depend upon the choice of a correct dosage for the individual patient. Due to variation in pharamacokinetic parameters, similar doses of a neuroleptic drug may result in different plasma levels in individual patients, especially after oral medication. Pharmacokinetic variations, if not under proper control, may easily disguise a concentration-dependent relationship, such as the effects of a neuroleptic drug upon negative and positive symptoms. In drug treatment of negative symptoms it may therefore be an advantage to individualize the doses as a function of plasma drug level measurements, when available. No general relationship has been demonstrated between the chemical properties or pharmacodynamics of neuroleptic drugs and their potential to act upon negative symptoms. Also, the drugs which have been demonstrated to have an “energizing” effect have widely different pharmacokinetic properties. A chemical or pharmacological classification of neuroleptics therefore does not seem to give any information about their possible efficacy in treating negative symptoms in schizophrenia.