Partial response of schizophrenic psychoses to a monotherapy with clozapine is a frequent problem of clinical psychiatry. Current problems are treatment resistant positive and/or negative symptoms, as well as side effects. Therefore, different strategies of augmentations have been applied. Based on successful experiences in case reports and results of other work groups, we aim to compare the augmentation of clozapine with ziprasidone or risperidone in a randomized, prospective manner.