We evaluated the effectiveness and the side effects of what we defined as low (5-mg) and conventional (25-mg) doses of fluphenazine decanoate administered every two weeks in a double-blind comparison. Subjects were 66 patients who fulfilled DSM-III criteria for schizophrenic disorder. Evaluation of the survival with each dose revealed no significant difference at one year, but significantly better survival was seen with the 25-mg dose (64%) than the 5-mg dose (31%) at two years. There was no significant difference in survival when the clinician was permitted to make a dosage adjustment up to 10 mg in the low-dose group and 50 mg in the higher-dose group when the patient demonstrated evidence of a symptomatic exacerbation. Patients assigned to the higher dose appeared to feel more uncomfortable during the early months of the study, as indicated by significantly higher scores on subscales of the Hopkins Symptom Checklist-90R and higher side effect scores for retardation and akathisia. Implications for clinical practice are discussed.