In a double-blind placebo substitution study, 27 chronic schizophrenic patients successfully treated for more than 2 years with fluphenazine decanoate were withdrawn from the drug. These patients showed a significantly higher relapse rate than the matched control group of 26 patients who continued to receive fluphenazine (56% versus 19%, p less than .001). This high rate of relapse is viewed as indicating the need for continued medication in most chronic schizophrenic patients.