The study aimed to determine if the addition of daily low-dose oral estrogen with a cyclical progestogen given to young women using a depot gonadotropin-releasing hormone (GnRH) analog implant for the treatment of their premenstrual syndrome (PMS) would affect the clinical outcome. In a double-blind placebo-controlled study in a specialist premenstrual syndrome clinic setting, 60 women aged between 20 and 45 years were randomized to one of three treatment groups: Group A (placebo implant four weekly + placebo tablets daily), Group B (goserelin 3.6 mg implant four weekly + estradiol valerate 2 mg daily with norethisterone 5 mg from days 21-28 of a 28-day cycle) or Group C (goserelin 3.6 mg implant four weekly + placebo tablets daily). Differences between PMS scores at 2, 4 and 6 months were compared with pretreatment values. There was a significant improvement in PMS scores in Group C (Zoladex + placebo) after 2, 4 and 6 months of treatment when compared to pretreatment values and Group A (placebo + placebo). The addition of a low-dose oral estrogen with a cyclical progestogen to GnRH analog treatment (Group B) resulted in a less dramatic response when compared to pretreatment values and no significant improvement when compared to Group A (placebo + placebo) at 2, 4 and 6 months of treatment. The addition of a low-dose oral estrogen with a cyclical progestogen to depot GnRH analog therapy in the treatment of PMS reduces the clinical response.