Background: Premenstrual dysphoric disorder (PMDD) is a severe form of premenstrual syndrome (PMS) that causes significant distress and interferes with normal functioning. Aim: The aim of this work was to assess the resting frontal electroencephalographic patterns in females who meet criteria for PMS and PMDD. Subjects and Methods: This prospective observational study was conducted on 150 female participants, of which 145 had PMS, and 45 were control women. All cases were counseled about the procedure. Furthermore, a written consent was taken from every patient. Cases were asked about their current phase of the cycle, in order to determine cycle timing. The custom PMDD interview involved asking each woman a series of questions concerning PMDD symptoms. This structured interview was created from the DSMâ€‘IVâ€‘TR criteria for PMDD. Women with PMDD were asked to complete a daily symptom rating checklist for three consecutive cycles. The ensuing methods were undertaken for each patient, including history taking, general, local and fundus examination, and routine investigations, and were submitted to resting electroencephalogram (EEG) examination during both follicular and luteal phases of the cycle. Results: Seventy percent of women with PMS and 75% of women with PMDD exhibited left frontal activity at rest, during the luteal phase of the cycle (P <0.001). Conclusions: We concluded that resting luteal phase of EEG frontal asymmetry must be added to the research criteria for PMDD (DSMâ€‘IVâ€‘TR).