The effects of folic acid on the oral mucosa of albino rats were histochemically studied in the twenty four male rats, weighing abut 100gm. Seven groups of 3 each were injected with 0.2ml folic acid (folic acid 0.5mg. was dissolved in physiological saline 0.2ml) subcutaneously, during 1,2,3,5,7,10 and 14 days respectively. Oral mucosa of rats sere removed from upper molar region and fixed in 10% formalin, cold absolute alcohol, Carnoy's solution and acetone. The serial sections were histochemically stained by McManu's PAS reaction, Mowry's metachromasia, alloxan-Schiff reaction, and azo dye method for alkaline phosphatase. The comparative staining method was hematoxylin-eosin stain. The results were as follows: 1) Alkaline phosphatase reaction of stratum spinosum and stratum granulosum tended to increase after 7 and 10 days of folic acid administration. 2) PAS reactions of basement membrane and lamina propria increased after folic acid administration. 3) Metachromasia of stratum spinosum and stratum granulosum were slightly increased after 3,5 and 7days of folic acid administration and returned to the level of Control after 10 days. 4) In the oral mucosa, alloxan-Schiff reaction increased after 7 days of folic acid administration.