Purpose: This pilot study was performed to understand the pharmacological effect of olanzapine, an atypical antipsychotic agent, on dopamine transporter in schizophrenic patients. Materials and Methods: Six patients (3 male, 3 female) with schizophrenia, who had not taken any psychotropic drugs for at least four weeks, were studied. Nuclear imaging using [^123I]-β-CIT SPECT was obtained before and after 4-week treatment with olanzapine. Anlaysis of ROI on the striatum, caudate nucleus, and putamen was performed. Results: Post-treatment uptake was significantly increased in all the ROIs compared with pre-treatment uptake. Conclusion: This preliminary study with the small number of schizophrenic patients suggested an increase in uptake of dopamine transporter in the striatum, caudate nucleus, and putamen after 4-week treatment with olanzapine, which warrants a large-scaled controlled study to confirm the current findings. (Korean J Nucl Med 2002;36;224-31)