Piquindone is an antipsychotic pyrroloisoquinoline derivative that binds to dopamine D2 receptors. It is a potent D-2 antagonist. It has a low potential for extrapyramidal effects and tardive dyskinesia. Piquindone exhibited relatively weaker cataleptogenic and antistereotypic activity than haloperidol, and had minimal activity in a rat chronic stereotypy model of receptor supersensitivity. Piquindone almost as potent as haloperidol, with fewer or less intense extrapyramidal effects and low potential for tardive dyskinesia. Piquindone led to moderate but significant improvements in the positive symptoms of schizophrenia and to improvements in negative symptoms just below the level of statistical significance. Therapeutic efficacy of a piquindone antagonist in Tourette Syndrome can be achieved without production of disabling extrapyramidal-side effects.