Malaria parasite requires a specific time to replicate and disseminate in the mosquito's body before transmission to naïve hosts can occur. Vector control has a proven record in the prevention and control of malaria. The evaluation of vector control strategies requires accurate methods of predicting mosquito age. Anopheles stephensi is the principal malaria vector of the desert part of India. The objective of this study was to correlate the age of laboratory reared and field collected adults of An. stephensi with the glucose-6-phosphate dehydrogenase (g6pd) activity. The measurement of g6pd activity was carried out in a UV-vis spectrophotometer. The g6pd activity in the males and females An. stephensi was inversely proportional to their age. A significant correlation of the g6pd activity was recorded between the field collected and laboratory reared mosquitoes. The g6pd activity in the males An. stephensi was found to be significantly higher than the females. The finding of the present study is useful for the prediction of the age of males and females An. stephensi.