Objective:To explore whether oxidative stress has any role in premenstrual syndrome(PMS). Methods:Female volunteers suffering from PMS,in the age group of 20-24 years were compared to their asymptomatic normomennorhoeic counterparts in follicular phase and late luteal phase for ferric reducing antioxidant power of plasma(FRAP),plasma protein thiols(PPT) and protein carbonyls(PPC) levels.Results:There was no significant change in FRAP and PPC levels in controls and PMS groups but PPT decreased significantly in luteal phase of PMS(P< 0.05) when compared to follicular phase.Conclusions:Estrogen and progesterone,might be responsible for a healthy antioxidant profile in PMS.However,a marked decrease in PPT in luteal phase of PMS group may be due to pro-oxidant nature of estrogen-active in this phase of PMS leading to consumption of the sacrificial antioxidant-protein thiol. Objective: To explore whether oxidative stress has any role in premenstrual syndrome (PMS). Methods: Female volunteers suffering from PMS, in the age group of 20-24 years were compared to their asymptomatic normomennorhoeic counterparts in follicular phase and late luteal phase for ferric reducing antioxidant power of plasma (FRAP), plasma protein thiols (PPT) and protein carbonyls (PPC) levels. Results: There was no significant change in FRAP and PPC levels in controls and PMS groups but PPT decreased significantly in luteal phase of PMS ( P <0.05) when compared to follicular phase. Conclusions: Estrogen and progesterone, might be responsible for a healthy antioxidant profile in PMS. However, a marked decrease in PPT in luteal phase of PMS group may be due to pro-oxidant nature of estrogen -active in this phase of PMS leading to consumption of the sacrificial antioxidant-protein thiol.