Specific Aims:
1. Evaluate the effects of single doses of sildenafil 50 \& 100 mg compared to placebo on cognitive functioning, including verbal memory, fluency, attention, spatial memory, motor speed, and executive function.
2. Evaluate the effects of single doses of sildenafil 50 \& 100 mg compared to placebo on psychotic, negative, and mood symptoms.
3. Assess self-reports of side effects of sildenafil 50 \& 100 mg.
Location and Subjects:
25 adult outpatients with schizophrenia will be recruited from the Massachusetts General Hospital outpatient clinic or the Freedom Trail Clinic of the Lindemann Center. All research procedures will be performed at the Psychopharmacology Clinic of the Massachusetts General Hospital. Subjects must be English speaking because the cognitive battery has only been validated in English.
