Sodium cyanate, a chemotherapeutic agent for Sickle Cell Disease, inhibits irreversibility of the sickling of erythrocytes from patients with this disease by reacting specifically with the NH2-terminal valine of the hemoglobin molecule without significantly destroying erythrocyte metabolism. It has been suggested that sodium cyanate may elicit neuropathology in pigtail monkeys, Macaca nemastrina. This study will provide information for development of further clinical studies for use in humans. Twenty adult animals will be divided into four groups: one as a sham and the other three groups will receive daily subcutaneous injections of sodium cyanate at 40 mg/kg; 25 mg/kg; and 15 mg/kg, respectively. Selected animals will be humanely killed and perfused for neuropathological examination at bimonthly intervals. Hematology, clinical chemistries, and neurological evaluations will be taken during the course of the experiment.