A case of transient granulocytopenia is reported during the seventh week of administration of TPS-23, a thioridazine derivative, in a patient who had received no medication for 59 days prior to the initiation of this new psychopharmacologic compound. However, the one occurrence of this serious toxic effect should not deter further evaluation of this compound which has obvious anti-psychotic and anti-depressant activity(1), unless additional evidence by other investigators reveals that the incidence of agranulocytosis is significantly greater with TPS-23 than it is with other phenothiazines.Abstract Teaser