OBJECTIVES: Bevacizumab (Avastin) is a promising and low cost treatment of age-related macular degeneration. Effectiveness and cost-effectiveness might be related to the frequency of injections of bevacizumab in the treatment. The standard frequency is 4 weeks, while it is uncertain whether lower frequencies lead to different cost and effects. METHODS: 170 patients were randomized to 3 treatment frequencies; 4, 6, and 8 week intervals between injections. Follow up was 1 year. Vision was measured with the Snellen chart, which health states have been valued for QALY analysis. We developed a 6 states Markov model with a 12 weeks cycle and a 6-year time-horizon. The model included one death state, and five states defined by visual acuity(VA) in the better seeing eye: VA > 20/40, ≤20/40 to > 20/80, ≤20/80 to >20/200, ≤20/200 to >20/400 and ≤20/400. RESULTS: At time of the (interim) analyses, 72 patients had completed the full follow up. The ‘6 weeks’ frequency compared with ‘4 weeks’ shows a negative ICER of €6.406, with €1,024 less costs and 0.16 more QALY’s. The ‘8 weeks’ frequency compared to the 4 weeks frequency shows also a negative ICER of €28,032, with €1.543 less costs and 0,06 more QALY’s. When looking at 6 and 8 weeks, the ‘8 weeks’ has lower costs but is also less effective, with an ICER of €4.946. Most uncertainty related to utilities and transition probabilities, while cost contributes relatively less to the uncertainty of the outcomes. CONCLUSIONS: Compared with 4 weeks frequency, the 6 and 8 weeks frequency were dominant, whereas the 8 weeks frequency has an ICER in the south west quadrant.