Background There have been many researches on Melissa Officinalis as an herbal medicine and have exceptional results, but there has been no proper research in homeopathy about its utility in PMS. We want to do this research to find in detail the utility of homeopathic medicine Melissa Officinalis in cases of PMS. Objective: 1. Primary objective is to study the effectiveness of homeopathic medicine Melissa Officinalis 200 CH versus homeopathic similimum in cases of premenstrual syndrome in females of age group 15-45 years. 2. Secondary objective is to assess the reduction in the intensity of PMS by using questionnaire. Method This study was randomized controlled trail. After identification of participants with PMS through the PMS questionnaire, they were assigned to Melissa Officinalis (n=23) and homeopathic simillimum (n=22) groups. Result A significant difference was observed in efficacy of Melissa Officinalis and homeopathic similimum incases of PMS. In this study, Melissa Officinalis was found to be effective in reliving symptoms ofPMS. Conclusion Melissa Officinalis is more effective than homeopathic simillimum in cases of premenstrual syndrome in females of age group 15-45years.