Abstract: OBJECTIVE To study the influences of fluvoxamine and cytochrome P450 1A2*1F(CYP1A2*1F) genetic polymorphism on the serum concentration of olanzapine in schizophrenia patients. METHODS Schizophrenia patients treated with olanzapine alone(the olanzapine group, 92 cases) and olanzapine combined with fluvoxamine(the combined group, 103 cases) were recruited. The blood samples were collected for the determinations of CYP1A2*1F genotypes and serum concentrations of olanzapine. Then the serum concentrations of olanzapine were compared between two groups, as well as among the different CYP1A2*1F genotypes. RESULTS The serum concentration of olanzapine in the olanzapine group (3.39±2.70)mg·L^-1·mg^-1 was obviously lower than that of the combined group(5.14±3.06)mg·L^-1·mg^-1(t=4.23, P=0.000). The serum concentration of olanzapine of AA genotype had an obvious decrease as compared with that of CC type the olanzapine group: (2.46±1.64)mg·L^-1·mg^-1 vs (4.42±2.88)mg·L^-1·mg^-1, P<0.05; the combined group: (4.06±2.65)mg·L^-1·mg^-1 vs (6.86±3.25)mg·L^-1·mg^-1, P<0.01. However, the serum concentrations of olanzapine were not significantly different between CA type and CC type. CONCLUSION Fluvoxamine may increase the serum concentration of olanzapine. The serum concentrations of olanzapine are different among CYP1A2*1F genotypes. Individual adminiatration of olazanpine based on the use of fluvoxamine and the genotypes of CYP1A2*1F is needed.