From a population of chronic schizophrenic patients receiving new psychotropic drug treatments, 48 were maintained on placebo medication for periods up to twenty weeks. Clinical pathological laboratory data were collected at the same intervals as in the drug-treated groups. While the range of laboratory findings was similar to the textbook standards, deviations ("abnormalities") were frequent. We conclude that each laboratory undertaking clinical drug evaluations should provide concurrent control data for placebo-treated subjects when reporting observations with novel compounds.