OBJECTIVES: Whilst the sight-restoring effects of surgery in patients with severe bilateral cataract are obvious, there has been a significant trend over the last two decades of performing cataract surgery at an increasingly earlier stage with a rising proportion having 6/12 vision or better at the time of listing. In these circumstances, the cost-effectiveness of surgery is open to question. Therefore, this study evaluated the cost-effectiveness of first-eye cataract surgery compared to no surgery from a Health Service and Personal Social Services perspective. METHODS: An economic evaluation was undertaken alongside a randomised controlled trial of first-eye cataract surgery in secondary care ophthalmology clinics. A total of 306 women over 70 years old with bilateral cataracts were randomised to cataract surgery (expedited, approximately 4 weeks) or control (routine, 12 months wait). Seventy-five percent of participants had baseline acuity of 6/12 or better. Health and social service contacts were collected at individual patient level from diaries ascertained at 3 and 9 months via telephone interviews, and at 6 and 12 months via face-to-face interviews. Outcomes included falls and Quality Adjusted Life Years (QALYs). RESULTS: The mean difference in cost between the operated and control group was £2004 (bootstrapped)(95% CI £1363 to £2833, p<0.001) over one year (UK£2004). However, those in the operated group experienced, on average, 0.456 fewer falls, representing an incremental cost per fall prevented of £4390. The bootstrapped mean gain in QALYs per patient was 0.056 (95% CI 0.006 to 0.108, p<0.001). The incremental cost utility ratio was £35,704, above the currently accepted UK threshold level of willingness to pay per QALY of £30,000. However, in a model of the costs and benefits over patients' expected lifetime, the incremental cost per QALY was £13,172, under conservative assumptions. CONCLUSION: First-eye cataract surgery, whilst cost-ineffective over the trial period, appeared cost-effective over participants' remaining lifetime.