OBJECTIVES: To measure the impact of periods on the lives of women reporting a problem, through the use of health related quality of life instruments in a real-world setting. METHODS: The evaluation was conducted throughout the United Kingdom using the web-based PROBE system (patient reported outcomes based evaluation). As women may not seek professional healthcare advice for this issue, recruitment was tailored to identify a sample representative of all women with problem periods. An initial screening questionnaire was used to programme the timing of the questionnaires (main evaluation). Questionnaires were completed around menstruation and mid-cycle in the same individual. Outcome measures included demographic data, symptoms, previous treatments, current medications, absenteeism, presenteeism, HRQoL using SF-36 and EQ-5D. Women with irregular periods or bleeding were not invited to the main evaluation due to difficulty timing questionnaire completion. RESULTS: A total of 2699 women participated in the screening questionnaire. 61% of screened women were under 30 years, half had sought medical advice and 25% were currently self-medicating for their periods. Patients were severely affected as noted on the following measures. Symptoms: 84% report physical symptoms, 78% psychological symptoms and 41% bleeding issues. Absenteeism: 21% take > 1-2 days off per month due to their period. Presenteeism: 33% reduction in workplace performance versus referent populations. 331 women participated in the main evaluation. From this, there was a significant difference in HRQoL between the worst and best times of the menstrual cycle: EQ5D questionnaire 0.57 to 0.76 (difference 0.167, p<0.001); EQ5D VAS 64.3 to 77.7 (difference 11.0, p<0.001); SF6D 0.61 to 0.72 (difference 0.1, p<0.001). CONCLUSIONS: This evaluation shows that women suffering from problem periods have a significant impairment of their QoL and productivity in spite of treatment.  A need exists for treatment that can alleviate these symptoms, enable more productive lives and improve the overall quality of life in these women.