Several years experience has now been gained in the use of needs-based measures in clinical trials and such use is increasing rapidly. This paper shows how four needs-based quality of life (QoL) instruments have proved effective in determining the benefits of interventions from the patients' perspective in clinical studies and trials. The instruments discussed are; the Quality of Life in Depression Scale (QLDS), the Migraine Specific Quality of Life Scale (MSQoL), the Recurrent Genital Herpes Quality of Life (RGHQoL), and the Quality of life-Assessment in Growth Hormone Deficient Adults (QoL-AGHDA).