This study was carried out to evaluate the effect of Er, Cr: YSGG LASER, CPP-ACP and their combination on the treatment of enamel white spot lesion after 24 hour and one month.A total of five freshly extracted intact human molars were selected. They were free of caries and fluorotic or hypomineralized lesions and any other visible defects, cracks, fissure, developmental lesion and/or restorations were selected. Teeth were then cleaned thoroughly and any plaque, calculus or any attached periodontal tissue. They were stored in saline solution at room temperature to be used within one month after extraction until the study was carried out. The coronal portion (Buccal and Lingual surface) of each tooth was divided into four standardized windows. The microhardness was measured for the control group (positive control) I0 in all specimens before any demineralization to be carried out. Then all specimens' windows were demineralized and the windows were divided into four classes demineralized (negative control) I1, treated with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) I2, treated with the Er, Cr: YSGG LASER I3 and treated with both Er, Cr: YSGG LASER followed by casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) I4, regarding time of storage in artificial saliva all these groups were considered as group one after 24 hours T1 and as group two after one month T2 with a total of 50 readings. Data were collected, tabulated and statistically analyzed.