There is growing evidence that long use of haloperidol and Olanzapine, a first and second generation antipsychotic drugs respectively have some variation effects on the renal function. Available reports seem to be conflicting, and also coupled with fact that these claims have not been sufficiently evaluated in our clime. This study was conducted to evaluate the effects of these drugs on renal function of schizophrenic patients being treated in Benin City, Nigeria. A total of 104 patients were recruited for the study. The 104 patients at the baseline comprises of 51(49.04%) males and 53(50.96%) females from whom baseline blood samples were collected as control samples, after which patients were placed on standard doses of Olanzapine or Haloperidol respectively and blood samples were collected at subsequent study visits being 1st, 2nd and 3rd months of drugs treatment for renal function test which comprises of urea, creatinine and electrolytes (sodium, potassium, bicarbonate and chloride) using a standard laboratory techniques. There were attritions along the line of study as some of the patients missed appointments while, others declined further participation. Of the 104 participants, 92 and 12 were placed on Olanzapine and Haloperidol respectively. The attrition rates for Olanzapine were 20.7%, 42.5% and 14.3% for visits 1st, visits 2nd and visits 3rd respectively while that for Haloperidol were 25%, 33.3% and 0% on the other hand. The ages of the participants ranges from 18 to 77 years, the mean age 37, with age group 28-37 are the most frequent (43.27%), while age groups 56-67, and 68-77 with 1.92% each were less frequent. Patients treated with Olanzapine were found to have sodium levels significantly raised from first month through the third months of treatment (p<0.0001), while bicarbonate levels were significantly decreased from second month to third month on treatment (p<0.05). Blood urea, creatinine, potassium and chloride levels were unaffected for both patients treated with Olanzapine and Haloperidol.