• To describe the spectrum and extent of disease in the population – e.g. what is the prevalence of human papilloma virus (HPV) infection among young girls?

• To identify factors that increase or decrease the risk of disease – e.g. what factors increase the risk of, or protect against, endometrial cancer?

• To study the natural history and prognosis of disease – e.g. does early diagnosis of cervical intraepithelial neoplasia (CIN) through cytological screening prevent future morbidity and improve survival?

• To monitor and predict disease trends in the population – e.g. what impact will the increasing prevalence of obesity in women have on future disease trends and healthcare needs?

• To provide evidence for developing public health policy and making regulatory decisions – e.g. will a smoking ban in public places promote smoking cessation and reduce the incidence of smoking-related disease?

• To evaluate the efficacy of preventive and therapeutic interventions – e.g. does postmenopausal hormone replacement therapy (HRT) do more harm than good?

• To evaluate public health programmes – e.g. will vaccination of schoolgirls against oncogenic HPV prevent vulvar/vaginal/cervical cancers and save lives?

• To evaluate the effectiveness of health services – e.g. are known contacts of persons with sexually transmitted diseases (STDs) followed up and treated?