The estimation of serum prolactin (Prl) and norepinephrine (NE) in chronic schizophrenics treated with neuroleptics for 5-25 years showed no elevated Prl levels in either men or women (4.9 +/- 4.1 and 13.7 +/- 12.1 ng/ml, respectively). No significant correlation to duration or dosage of neuroleptic treatment, psychopathological syndromes and occurrence of tardive dyskinesia or parkinsonian side effects could be seen. The development of tolerance of the tuberoinfundibular dopamine system is discussed. The NE levels were distinctly elevated in both sexes; in men up to 0.77 +/- 0.4 and in women up to 0.90 +/- 0.48 ng/ml. This elevation is induced rather by neuroleptic treatment than by external factors. A significant relationship between dosage or duration of anticholinergic treatment and the severity of tardive dyskinesia was found in men.