OBJECTIVES: Accurately assessing changes in the quality of life of elderly people is becoming increasingly important. Generic instruments are the most popular method by which to assess quality of life; the EQ-5D in particular for economic evaluation. However, this instrument has been criticised as having insufficient dimensions, insensitive scales and concerns over completion rates. A possibly promising new alternative appeared to be the Assessment of Quality of Life (AQol) instrument developed in Australia. This purported to offer greater richness in dimensions, and sensitivity to small changes in quality of life. We describe a "head-to head" comparison of the EQ-5D and AQol. METHODS: As part of a large trial investigating domiciliary medication review, the 2 instruments were used to assess changes in health status in 145 patients over 80 years old. Questionnaires were administered by researchers at baseline and by post at three months and six months. This study describes: (a) the practicality of using the questionnaires; (b) test performance, in terms of construct validity and internal consistency; (c) agreement of instruments, in terms of absolute utility scores and changes in scores over follow-up; and (d) sensitivity to changes in health status. RESULTS: The EQ-5D proved easy to administer with good response rates to postal follow-up (81%). 15% fewer AQol questionnaires were returned fully completed (95% CI 12-19%). The construct validity appeared to possibly favour the AQol. However, over 6-months follow-up the EQ-5D changed by 0.16 units versus AQol change of 0.12 units (95% CI -0.14 to +0.003). Whilst the EQ-5D showed moderate sensitivity (effect size of 0.52) the AQol appeared to be poorly sensitive (effect size of 0.34). CONCLUSION: The results of the analysis presented in this paper suggest that the EQ-5D is a practical and sensitive tool with which to assess quality of life within the elderly.