[en] Optically Stimulated Luminescence Dosimeter (OSLD) type penlight (XA) was introduced in Malaysia in 2011. Four years later it has become a major tool for monitoring of personal dose of 18,000 radiation workers in Malaysia. This paper aims to examine the effects produced storage period of reading OSLD. In this study 15 units OSL dosimeters were used in which 3 units are used as a control, while the rest is radiated to 4 different doses of gamma radiation of 0.1 mSv, 0.5 mSv, 10.0 mSv and 5.0 mSv using Cs-137 source. For each radiation dose, 3 units OSL dosimeters were irradiated. Dosimeter readings taken using a reader Landauer - Enlight Auto 200 Reader (No. series: Model: Auto 200; Serial No.: 10720081) and the readings are recorded every month for a period of 16 months starting on Feb 19, 2014 to June 5, 2015. The results obtained indicates that the storage period can cause significant changes to the OSL dosimeter readings. For the dosimeter control, the readings found to have increased by an average of 0.11 mSv per month. While the dosimeter is irradiated, found reading is declining but the rate of decline is dependent on the value of the exposure dose is given. (author)