Based on recent quantitative EEG findings of increased slow activity in negative schizophrenia indicating organicity, it was hypothesized that neuroleptics decreasing delta/theta activity should be beneficial for schizophrenics with predominantly negative symptoms. Thus, a double-blind, clinical, psychometric and neurophysiological study was carried out in 40 hospitalized patients with unproductive schizophrenia (mean age: 31 years; ICD diagnoses: 295.0, 295.1 and 295.6) who were treated randomly either with the benzamide amisulpride (AMI; n = 19) or low doses of fluphenazine (FLU; n = 21). In the first 2 weeks the daily doses were 50 mg AMI or 2 mg FLU, respectively, from the third week on up to the sixth week 100 mg AMI and 4 mg FLU. Clinical evaluations, psychometry and EEG mapping were performed on day 1 (hours 0 and 4--acute effect), on day 14 (hour 0--subacute effect) and on day 42 (hours 0 and 4--chronic and superimposed effects). Three AMI patients discontinued therapy prematurely because of productive symptoms (days 14, 28 and 35), while in the FLU group 2 patients dropped out due to depressive symptoms (days 21, 28), 1 due to productive symptoms (day 35), 1 due to ineffectiveness (day 28), and 1 because of an akinetic crisis (day 6). Statistical evaluation demonstrated a significant improvement in the AMDP apathy and Andreasen SANS score in both groups with the patients remaining severely ill as rated by the CGI. FLU-treated patients needed significantly more anticholinergic medication than the AMI-treated group. Psychometric evaluation showed in regard to the noopsyche significant improvement after subacute, chronic and superimposed AMI, while FLU-treated patients showed significant improvement only after subacute treatment. AMI was significantly superior to FLU at the hours 0 and 4 of day 42. The thymopsyche improved after subacute, chronic and superimposed administration of both compounds with a significant superiority of AMI on days 14 and 42 (4 h postdrug). EEG mapping showed a decrease of delta/theta and increase of beta activity as well as an acceleration of the centroid after acute and superimposed AMI on day 42 as compared with baseline; FLU patients exhibited a decrease of delta/theta activity and an acceleration of the total centroid too, while alpha activity was augmented and beta activity tended to be reduced. Our study demonstrated that, in addition to the new benzamide AMI, FLU in low doses may also be regarded as a neuroleptic with activating properties and may be utilized in the treatment of schizophrenics with predominantly negative symptoms.